Very little is known about Eileen's personal life, other than she had a daughter named Sheila and raised her on her own in Nashville, Tennessee. In 2009, when Sheila was eight years old, she was abducted by Michael Thompson and had never been found ever since, leaving Sheila to live a life of pain and fear for her daughter's safety. Little did she know that Sheila was being held captive by Thompson, who physically and sexually abused her and tortured her for years.
Eileen is first seen in the hospital being interrogated by Hotch after Sheila is rescued. She tells Hotch about the day she received a call from school, informing her that Sheila disappeared. She then wonders who abducted her daughter and tortured her. Hotch replies that he and his team are trying to find that out. Afterwards, Sheila suddenly begins coding and the doctors and nurses rush to her room to help her. However, by the time they try to save her, it is too late and Sheila dies, which devastates Eileen. Later, JJ introduces her to Gina Bryant, another girl who was abducted by Thompson; Gina apologizes to her and says that she tried to help Sheila. She is next seen looking angrily at Thompson while he is being taken down the hallway. At the end of the episode, as Thompson is taken out of the hospital, Eileen shoots and kills him with a revolver she somehow retrieved. Afterwards, Hotch arrests her while she bitterly watches Thompson succumbing to his wounds.
Since she only killed Thompson, the term "M.O." is misused. When she killed him, she shot him once in the chest with a revolver.
- February 10, 2016: Michael Thompson
- Eileen is extremely similar to Monica Kingston, a character who appeared in Season Seven. Both had daughters who were abducted by preferential offenders and held captive by them in a span of years. Their daughters were also sexually abused and eventually impregnated with their captors' babies, though the pregnancies were somehow unsuccessful and the babies died. In addition, their daughters eventually died in some way relating to their captivities. In the end, both Eileen and Monica shot and killed their daughters' abductors out of revenge.