she also has a competitive streak a mile wide, and fortunately for her, is quite good at what she does; i think the reason she’s still alive is that her desire to win keeps getting the upper hand over her desire to self-destruct.

Huh. That actually ties back into her actions during the flashback of "the boxing episode". Lee, for the best of reasons and with the best of intentions, got briefly into a position of dominance over her (emotionally -- I think it's no accident that she was on top physically during the sex!). As soon as she had a non-endorphin-laden moment to think, she reacted in a way that would define him as the "loser" and herself as having "won".

As long as she reacts to life that way, she'll *never* have a healthy relationship. Because love, *real* love, isn't a zero-sum game.