Why is it that everytime my girlfriend gets too drunk, she keeps.....?

pushing me away saying she doesn't need my help, she keeps thinking im going do something bad to her, says she doesn't need me and acts somewhat distant as if im a stranger...but theeen when i let her be...she comes and apologizes trying to be all cute...hugging me and all that...and then she goes back to being beligerent and somewhat of a brat..then back to being sorry...im confused..we've been together for about half a year and i've respected and treated her right. at first i thought it was just drunken antics..but now im thinking there's a psychological aspect. is she suppressing something?