Lisa Marshall is a character in DEXTER. She is the older sister of Travis Marshall, whom she rarely gets to see now due to his "work". She is a teacher at an elementary school and her personality suggests that she is a really kind person, and very caring of her younger brother.
Lisa is very caring toward her younger brother, Travis. The fact that he is always working is very 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 to Travis when he says he only has an hour to be with her before going back to work.
Lisa is first seen working around her house as Travis comes in, unnoticed. As soon as Travis touches her shoulder, she becomes startled, exclaiming "God damn!". Travis tells her he wishes she wouldn't say that, but they still sit down to dinner. During their dinner, Travis eats very fast because he has to get back to "work".
However, she persuades Travis to stay for dessert. When Travis comes to Gellar late, Gellar places a hot iron on his own wrist, and Travis begs him to stop. He tells Gellar he won't go see his sister again, and Gellar removes the iron from his own wrist. After that, Gellar tells Travis it is not her job to take care of him, it's Gellar's.
She appears again, in Just Let Go, teaching a class of elementary students. When Travis shows up, she becomes excited, and introduces her class to Travis, telling them all that he is an artist himself.