sould we break up

Just kissing other girls does not mean that she is a lesbian. It may be out of fun, love or affection. But you have to keep a constant watch on her behaviour towards other girls before coming to the conclusion of her being a lesbian. At the same time you should watch her reactions on your doing the same with your male friends. But in spite of all these, if you come to the conclusion that she is a lesbian I would suggest you to make her understand that this relationship is not healthy at all and so should be rejected. If all these measures fail, it is better to break the relationship.

i think your girlfriend's just experimenting. you should tell her how you feel, that it's making you feel uncomfortable. if you want her to stop, then tell her. if she doesn't consider your feelings, then you really should think about breaking up with her.

I would ask her how she would feel about you kissing other guys. If she wouldn't like it I would say that would make your case.

Haha...A terrible thing to see your girl friend kissing a girl too. Maybe she is not a lesbian but the other one is a lesbian. That's not a normal thing for a girl acting like that, my friend... If I were you need to thinks now and decide... Have a nice day!