Just a quick question.

A few more details?

Are you a girl and she is cheating on you ?

Quick questions are hard to answer.

We need some more information please.

Uhm, you should.. talk to her about it? She was probably under an influence, and if she's gay then its her discicion, but she shouldn't be doing that while she's your girlfriend, if she's cheating on you(girl) with another girl. Then that's just rude. Anyway, confront the problem, ask her about it, get some answers!

What did she tell you? Was she drunk??

If it makes you uncomfortable then tell her so. If you don't voice your opinion then how is anyone to know what bothers you and what doesn't?

Talk to her about it. If something bothers you - talk about it. Than you can make your decision.