She was portrayed by Erin Chambers from September 15, 2010 to November 16, 2011.
Siobhan was first introduced when Lucky Spencer is undercover in Ireland as Ronan O'Reilly. He is drinking at a bar when Siobhan storms in, slaps him, and accuses him of killing "her Donnie". Donnie's brother comes in and starts a fight with Lucky, but Lucky gets the upper hand and lets the man go. She wonders who he really is, as Ronan would have never let a man live after provoking him like that. Lucky dodges the question and brings her back to his apartment. She pulls a gun and asks him again who he really is. Lucky comes up with a story about how he found God, and she tells him she wishes it would have happened sooner so Donnie would have been spared. Later that day, she comes back and informs him that some Slavic men were asking about him at the bar. She kisses him and leaves.
A few days later, she walks into the bar and sees Dante Falconeri and Lulu Spencer sitting there. She hears them asking about Ronan and joins them. Lucky comes in after being held prisoner by the Balkan's men and notes the interesting group. Lulu and Dante claim to be police officers. Later that night, when Dante and Lucky are meeting with the Balkan's men, Siobhan stops by Lucky's place and finds Lulu instead. They chat for a while and it becomes evident to Lulu that Siobhan is falling for Lucky. Dante texts Lulu and she leaves. Siobhan hides in the closet as Lulu, Dante, and Lucky return. She overhears their conversation and learns that "Ronan" is really an undercover cop. Lulu, Dante, and Lucky leave and Siobhan leaves shortly after, running into Lucky in the hall. She glares at him and leaves. They run into each other in an alley later that night and she lashes out at him for lying to her. He comes clean with her but she disregards him.
After a short stay in an Irish prison, Lucky meets up with Siobhan in his apartment. He tries to explain things to her and tells her that he genuinely likes her, but she calls him a liar. Before she can leave, though, he pulls her in for a kiss, but Siobhan knees him in response. On a pier in Ireland, Lucky meets up with the Balkan's men. Siobhan spies on their conversation until she is discovered. Lucky tells the men to let her go as she is helping him with his assignment to kidnap Brenda Barrett. Once they let her go, Lucky and Siobhan go back to his apartment. He tells her that she is coming with him to Rome. She argues, but he tells her if she stays, she'll be killed. She reluctantally agrees and the two head to Rome.
Once they arrive, Lucky gets beaten up by the cops and Siobhan patches him up. When she's done, she kisses him. He doesn't respond at first because he doesn't think he should. He explains his romantic history to her, but she tells him that she's not searching for marriage, she just wants to sleep with him. They do, and the next morning Lucky starts to leave the room, but Siobhan wakes up and accuses him of sneaking out. He tells her he's just going out to look for Brenda, but she wants to go with him. While at the hotel Brenda was staying at, Lucky finds out that Brenda went to Port Charles. Some of the Balkan's men come up and grab Siobhan, instructing Lucky to shoot her. Lucky raises his gun, but reminds the men that they are out in public with witnesses all around. While he is distracting them, Siobhan manages to break free. He returns to their hotel room and finds Siobhan inside. He tells her that he is taking her to Port Charles for her own safety.
Nikolas is looking over papers at Wyndemere when Lucky comes in and introduces him to Siobhan. They arrange for Lucky and Siobhan to stay with Nikolas. While Lucky is talking on the docks with Jason, Siobhan and Nikolas talk at Wyndemere. Siobhan notes that it doesn't seem like Lucky's kind of place, and Nikolas tells her its not really his style. When Elizabeth stops by, she hides behind a cabinet since no one is supposed to know she's alive. Elizabeth informs Nikolas that she lost all of the boys' trust fund money. He offers to help her, but she doesn't want to cause more tension between him and Lucky. Lucky comes back and wonders what they're discussing. Nikolas leaves and Elizabeth explains how she lost all of the boys' money. Lucky assures her that he will help and she leaves.
Siobhan comes out and tells him she overheard everything and she wonders why he would care. She points out that their relationship is based on danger, but he tells her they may not be on the run for much longer. They talk about her going back to Ireland, but Lucky tells her it's too soon to talk about her leaving and that she's still in danger. She tells him that she can take care of herself, and Lucky wonders why she's so determined to get away from him. Lucky gets a call from Lulu and she asks him to meet her on the docks. They talk about Luke's plot to get Tracy to marry him, and Swavek, one of the Balkan's men, discovers that "Ronan" is really an undercover cop.
After visiting his dad in the hospital, Lucky returns to Wyndemere and tells Siobhan about Luke and Tracy, and also his conversation with Jason. She asks him if he trusts Jason and he says he does, but she tells him that you have to be careful because you never know what secrets people are keeping. He tells her about his plan with Jason and instructs her to wait there. She tells him that she thinks he will walk right into an ambush. After Lucky leaves, Nikolas tries to reassure her and leaves to go trick-or-treating with Elizabeth and the boys. Siobhan takes off and is taken by one of the Balkan's men. She is questioned about Ronan O'Reilly's true identity, but claims that she works for Nikolas. The man doesn't believe her, though.
Lucky, Dante, and Jason are contacted with information about a proposed trade between Brenda and Siobhan. Jason is initially hesitant, but Lucky and Brenda push him to agree, planning to set the Balkan up. Lucky, as Ronan, brings Brenda to the woods with Jason and Dante hiding behind the trees. Jason instructs Dante not to shoot, but when he hears Brenda scream, he shoots at the men. All of the Balkan's men end up dead and Jason brings Brenda and Siobhan back to his penthouse. Jason questions them and Siobhan tells him the man had instructions to get Brenda alive. She leaves the penthouse and goes to Lucky's apartment. He tells her he won't let anything like that happen to her again, but she tells him she doesn't need his pity or his help. He tells her that she's an adventure that he wouldn't have missed for the world.Lucky wakes up the next morning and finds Siobhan packing to go back to Ireland. He tells her it's not safe for her to leave and that he would miss her if she does. She reminds him that she lives in Ireland, but eventually agrees to stay in Port Charles, as long as she takes care of herself. She says the first step is finding a job, so she heads to Jake's and meets Coleman. After a brief interview, he hires her. Her first customer is Maxie who learns that Siobhan has an interest in Lucky. After Maxie tells him about her conversation with Siobhan, Lucky goes to Jake's and flirts with Siobhan.
In early 2011, it is revealed that Siobhan is working for the Balkan, a well known criminal. She goes to meet with Jerry Jacks, whom she thinks is the Balkan, and witnesses him get shot by one of the Balkan's men, revealing to her that he wasn't the Balkan. From then on, whenever she would knowingly meet with him, it would be in a church confessional to conceal his face.
Lucky eventually finds out that she works for the Balkan after he gives her the name of a church, telling her that is where Sonny Corinthos and Brenda Barrett will be getting married. He finds her taking photos of the church, intending to send them to the Balkan. She initially denies having any ties to him, but she eventually tells Lucky that he is forcing her to work for him by holding her sister Megan hostage. The two plot to set the Balkan up and during Siobhan's next meeting with the Balkan, Lucky follows her to uncover the Balkan's identity. One of his men, though, finds Lucky, knocks him unconscious, and ties up Siobhan. By the time Lucky regains consciousness, the men have already left. He hears Siobhan's screams and unties her. They know that the Balkan suspects she is being disloyal.
Siobhan fears for her sister's safety and Lucky comes up with a plan. When Siobhan goes to work at Jake's, Lucky comes in and arrest her as one of the Balkan's men, Shawn, watches. As they leave, Shawn calls the Balkan and assures him of Siobhan's loyalty. Lucky brings Siobhan into the interrogation room at the PCPD and Theo Hoffman, who is secretly the Balkan, comes in and tells Lucky to release Siobhan. Lucky takes Theo out into the lobby and tells him that he plans to keep Siobhan in questioning as long as he can—48 hours. Theo sits down and Lucky goes into the back. He and Siobhan, who is dressed in a police uniform, sneak out without Theo noticing.When they get back to Lucky's apartment, Lucky asks Siobhan if she remembers anything from her phone conversations with Megan. She tells him that se heard bells—the same bells they would hear at the boat launch. He tells her to get ready because they only have 48 hours to save her sister, but Jason shows up and tells them that they aren't going anywhere. She would be poisoned by Anthony Zacchara and is seen last in Lucky's dream in November 2011.
- Spied for Theo Hoffman (aka The Balkan) [2010-11]
- Slapped Lucky Spencer [Sep 15, 2010]
- Kicked Swavek, one of the Balkan's henchmen, in the leg in self-defense [Oct 19, 2010]
- Fraud; married Lucky Spencer to keep from being deported [Mar 2011]
Health and Vitals
- Manhandled by one of the Balkan's henchmen [Oct 12, 2010]
- Swavek held a gun on her [Oct 18-19, 2010]
- Abducted by Marko, one of the Balkan’s henchmen [Nov 1-9, 2010]
- Held at gunpoint and threatened by Jerry Jacks [Dec 17-20, 2010]
- Hospitalized after being trapped in a burning house (suffered a few minor injuries as well) [Jun 16, 2011]
- Accidentally had the wrong medication injected into her IV (during surgery) by Elizabeth Webber, which caused her blood pressure to drop and she almost died [Jun 20, 2011]
- Had a nose bleed [Jul 29-Aug 1, 2011]
- Fell down a flight of stairs while arguing with Elizabeth Webber [Aug 5, 2011]
- Hospitalized after a car accident (she was thrown from a car driven by Elizabeth) [Aug 5, 2011]
- Died after being poisoned by Anthony Zacchara [Aug 22, 2011]
- Full name stated on March 18, 2011.