My GF's Male "friends"

i hate my gf's male friends and how she acts towards them. ALL....yes let me say that again...ALL of her male friends have either had sex with her, asked to have sex with her, dated her, or had a thing with her. my gf is 15, they are all no younger than 19. i think it is messed up. she posts stuff on facebook about them using smiley faces and hearts and tagging them. she ignores me to talk to them. she blows me off to hang out with them...even though several of these guys have to go behind their gf's backs to hang out with MY gf. she's always texting one of them. she says shes grown up with them all however under these circumstances i do not believe they're true friends, especially seeing as they're my friends too and before we were together all they did is talk smack about her and say shes a slut. Ive told her this several times and she says they're just friends. Ive also told her i don't like it and honestly it hurts me every time i see stuff on Facebook or they hang out, and she flips out and doesn't seem to care and says shes not losing her "friends" for a guy. am i crazy or is she an a**hole? i need advice :(