Gf pussy farts when she says she busted, don't believe her?

O.K. I really need some opinions on this...Its been one year after we went out...and we have sex every now and then...thing is she said she was a virgin before we started fukin, she was 15 last year and now 16. We started fukin about two weeks after going out, she said she was a virgin back then, and whenever I go over to her house, we fuck! When she comes to my house, we fuck! Up until four months after, we started to explore a bit, she bent over and I did her pussy from the back(doggie style). I was gentle at first, but her moaning just kept me going harder and faster, after a few minutes, her pussy farted upon my dick(felt kinda god). She told me she kinda busted "she thinks"...its been four months and she says my dick was the only one she ever inserted into her holes(mouth, pussy, butt)...but hearing from some sources that farting pussy during sex is a sign that she has had sex more that a few times before and during our relationship. She broke mine, it would feel a lot less shitty if she did the same. 4 months fucking made her pussy fart like that or is she fuking some other fuckhead the same time. Just need some verification that she was a decent virgin girl until she met me.