I think Starbuck’s behavior is right in character. You’ve got a rough 'n tumble, love 'em and leave 'em guy type chick who fell for someone a lot harder than she thought she would, then had to break a promise to come back, which doesn’t go well with her self image as the “I can always pull victory outta my ass somehow, and the worse the odds are the better I like 'em” hotshot.
Then she has to deal with the whole Pegasus thing, the initial uncertainty and unease about the changes to the fleet and personnel–gets promoted to a job that’s so perfect for her and so much up her alley it isn’t funny, and by a CO who with slightly different circumstances could be the one person she could look up to more than Adama, then her father figure tells her to A) go against everything a soldier IS by fragging a superior officer–and on the bridge no less; and B) KILL that person who with slightly different circumstances could be her perfect mentor.
Okay, so that doesn’t happen, the pressure is off. Unfortunately for the tightly wound, risk loving personality, having the pressure taken off is often the very worst thing that could happen. Suddenly there’s all this time to THINK and REMEMBER and HATE YOURSELF FOR FUCKING UP, and this type of person is SO not good at regulating her own behavior from inside–that’s what risk and pressure are for, to keep her from flying apart.
So she goes for what she knows, drink until your head shuts up, get laid a bunch to take care of those nagging little urges (it couldn’t possibly be that she only wants to get laid by one certain guy, oh no, that would be too much like mushy love or something!) and shoot some bad guys.
Problem is, she can’t drink enough to shut up her head, she IS grieving over losing someone, and there’s a part of her that hates herself for being willing to frag her CO and for being so damned relieved she didn’t have to do it, and part of her kinda sorta thinks how nice it would be if she just kinda lost it for JUUUUUST long enough for that legendary Cylon raider Scar to take her out–it’s a hero’s death, right? Nobody would look down on her if she got taken out that way–when she was naming the list at the end, she was accepting the fact that she herself wasn’t on that list and it’s maybe okay to keep living.
This ep is all about redemption.