Tina is a one-time character who appears in "Last Chance to See Those Tattoos ", and was one of Charlie's ex-girlfriends whom he apologizes to.
Background
Tina is the first ex-girlfriend/fling that Charlie apologizes to. When he shows up at her door step, she ask him what does he what. Charlie wanted to apologize for ending things badly. Tina thought they ended things "perfectly", explaing how they once spent a week in Cancun, having great sex every day, and when they flew back to Los Angeles, he told her he'd call her tomorrow and it has been a year-and-a-half since he promised he'd call her. She compliments him, saying that time flies when Charlie's the scum of the earth. Charlie tells her he's sorry he didn't call her soon enough and she believes him. She invites him into her apartment for coffee and asks him if he's seeing anyone at the moment. They end up sleeping together, which she says was "a fun apology" and asks him if he will call her. Charlie says he will count on it, but it's obvious he won't.
Trivia
The actor who plays Tina, Jennifer Bini Taylor, played a major recurring character, Chelsea, later on in the series.