Girl With Fire
I think that of recent bisexuality has become the in thing, kinda like celebs and flashing themselves or going to rehab. Bisexuality or Homosexuality with women is a lot more accepted these days and it's more publicized and it's more accessible in the media and can even be found in entertainment directed at teenagers.

I think that with that mentality there are more people who want to be crowd pleasers and fit in so they do these stunts like making out or hooking up with girls while out partying and they get to be "that girl" who is fun and sexy and popular.

It can also be that while under the influence they can say or do things that they wouldn't do while sober and blame on being under some sort of influence (alcohol, drugs, the high from just being in a club atmosphere). It's possible that the thoughts and fantasies and desires were always there and weren't acknowledged or only subconscious and being out and being able to blame whatever is being done or said on being under the influence provides a "safe" way to act on those thoughts, fantasies or desires. And then once they sober up they can say that it was because they were intoxicated.

I myself am openly bisexual and I find it annoying and frustrating when you meet men who I like in a platonic sense, but they're just waiting for the chance to see me make out with my girlfriend. I also hated when I may really like a girl and they're only hooking up or making out with me because it's a turn on for the men around them or for whatever nonsensical reason. I once heard a term on the Tyra Banks show called Bar-Sexual applies there. It refers to women who only hook up with other women while inebriated at a bar or club just to be a crowd pleaser.

J's Alley
I can totally see your frustration with someone trying to force a label on you. I can see how she might think you were just in denial and she was probably trying to honestly help you out of the closet. I'm not saying either of you were right or wrong, but I can definitely see both sides.

If it wasn't for the fact that this only happened while you were out and about and probably somehow inebriated I would say you could identify with a character on The Real L Word. She didn't want to be labeled as bisexual or as being attracted to men or women - she felt she was attracted to the person regardless of their sex. The character (Jill I believe) identified with this book Sexual Fluidity: Understanding Women's Love and Desire. A quote she said in an interview was "I would encourage all young women to allow themselves the freedom to explore their sexuality, without fear of stereotypes, definitions and labels. Sexuality is such a tremendously complex concept. To me it feels very narrow minded to try and package attractions, emotions and experiences neatly into a box. Too many factors are at play when individuals feel for one another, and moreover those feelings can easily change over time as we grow. The concept of fluidity affords a flexibility to our attractions, understanding that they can change based on an array of situations. I hope that young woman can avoid the societal pressures of having to ‘declare’ a sexual identity (if one doesn’t perfectly fit) and instead, simply experience happiness and love where, when and how they find it." I don't know if that really applies to you, but when I read your post that's what I thought about.