<human>: Can you summarize the given text in a few sentences?

My girlfriend had been really weird and distant since I'd been out of town for two weeks at the beginning of this month. She's always really protective of her phone but when she fell asleep way before me last night, my drunken curiosity got the better of me and I looked. I found out that there was this guy like 1000 miles from where we live that she'd basically been sexting with on and off for like a month, skyping and snapchatting with him too but obviously never actually doing anything sexual because he doesn't live anywhere near here. No affection or boyfriend stuff or anything, purely sexual. Not that that excuses it at all.

I haven't brought this up to her. I left since she was already asleep and just told her when she woke up and texted me this morning that I had somewhere I had to be early. But idk what to do about this. It wasn't classic cheating, and I don't think she's the type to physically cheat anyway. But this isn't cool. I'm just at a loss. What should I do?
<bot>: girlfriend exercising fantasies over internet with some guy she's never met and never going to meet but it's still pissing me off and I'm not sure how to feel about it