A fellow bsg fan described her to me as being consistently inconsistent, which I think fits her to a tee. Nothing she did in the show, however unconventional or unethical, were ever wrong in the end.
And that's part of my problem with the show as a whole. Everyone is always so quick to blame Lee for his mistakes (both the other characters and the other fans, sometimes), yet Kara gets forgiven no matter what (as does Helo).

Consistently inconsistent fits the bill, all right. :)

When two people profess love for each other, in that intimate manner, whether or not alcohol was involved, things had already started, big time.
Things had started and I'm sure she must have seen it coming for a while. But, they hadn't gone public yet, hadn't even admitted to themselves. And there, yes, they did acknowledge their feelings, but they didn't go public with it, and I think it makes a difference. Announcing the world that you're in love with someone else takes it to a level of commitment she wasn't ready for; it would have made things more real than they were.
That's how I fanwank it, anyhow.

She doesn't know which men she loves more, but she sensed Anders is easier to..."control" (for lack of a better word), and more prone to turn a blind eye to what she does.
Not sure about the control part, but it's true that he's... paler, than Lee, somehow. He's not quite as obstinate, not as strong willed and strong minded, not quite a match for her. I think she also was scared of how strong her feelings for Lee were; it left her vulnerable, and she doesn't like that, so she tried to take control back by leaving first.

I could be wrong, but I've always thought they retreated to the SPACE outside the colonial space, not a planet.
I'm really not sure. I always pictured a planet in my mind, but I can't be sure whether it came from the show, or not...