You fucked up on a few levels man.
1. If you're trying to have a successful relationship, you never EVER discuss any problems with another bitch other than your own. Your homies are cool, but to another bitch, you fucked up, you pretty much told your ex that your current bitch needs some get-right. That would have been not an issue had your bitch NOT find out. She went through your cellphone and you got caught slippin. Clear your damn cookies too!
2. You also did some simp shit, you let a bitch tell you about her dudes problems and probably talked back and forth about it. That shit is a man code violation. If your chick was talking about you not being this or that, you would be heated and felt crossed. Not to mention bitches are vindictive as fuck, and need their daily dose of drama to get through the day, you said it yourself, she probably wanted to get after it.
As a dude, I can agree that if you ain't boning then you haven't cheated. But you obviously should know by now that bitches do not think this way lol. This broad is always going to rub your nose in this shit.
Step your gat damn Dr. Phil game up.