Here is the deal, She's one of those "oh boy do i love attention" girls, i know because I've dated one and I'm telling you they don't care about your opinion, feelings and wether or not she kissed someone else.
these girls only care about themselves, getting attention being treated nicely they say that they won't ever break up, you put your heart and soul into the relationship while if they don't feel good for a while they are just going to leave you, they desecrate themselves in some social groups but she will be prolly part of a so called "slut group" who do nothing else then bragging about shagging the "cool, hot or popular' dudes, and if you're not one of those i think your girlfriend probably never talks about you when these other girls are around. my advice is to dump and forget, i know you'll think this is stupid because you love her so much but believe me you're gonna put yourself through much more if you stay with her.
tl;dr Dump her for your own sake, this girl is a common slut.
