Carley, because she and Lee had the very beginning of a relationship when Lilly shot her. She saved his life twice, then he saved hers (dependent). Plus, the fact that she trusted him enough to keep his secret.
Lilly was never an option until Larry had died. Plus, she just felt a little too "we do this MY way"-ish for my Lee to even be her friend, then again, my choices probably affected my view of her.
Molly is a bit too much of a loner for there to even be a relationship possible. Christa is too judgemental and overbearing, while Katjaa is already married. Those two would be like Lee's wife and the senator, with Kenny playing the part of "angry Lee" when he found out. He never had a chance with Brie, as she was the contest winner and was going to die no matter what.
Since all of those people are either dead or gone, looks like Lee is going to be a bachelor for the rest of his (very short) life.