She is the older sister of Travis Marshall.
She is a teacher at an elementary school and her personality suggests that she is a kind person, and very caring of her younger brother, Travis. The fact that he is always working is upsetting to her, and she wishes that he would spend more time with her. Apparently, they spent a lot of time together in the past, indicated by what she says when he tells her that he can only stay with her an hour before going back to work.
Lisa is first seen in her house as Travis quietly comes in, unnoticed. When Travis touches her shoulder, it startles her and she exclaims, "God damn!" Travis rebukes her, saying he wishes she wouldn't say that, but they still sit down to dinner. Travis eats very fast because he has to get back to "work." However, Lisa persuades Travis to stay for dessert. she rarely gets to see now due to his "work."
When Travis goes to Gellar the night, Gellar places a hot iron on his own arm, and Travis begs him to stop. He tells Gellar that he won't see his sister again, and Gellar removes the iron. After that, Gellar tells Travis it is not his sister's job to take care of him, but Gellar's.
Lisa appears in "Just Let Go," teaching a class of elementary students who are drawing pictures. When Travis shows up, she becomes excited, and introduces her class to Travis, telling them that he is an artist himself.