<human>: Can you provide a brief overview of the text?

Concerts aren't really my thing, but my girlfriend loves them and usually goes to one or two every month or so. I've never had any reason to suspect her of cheating but last Sunday after a concert she texted me at 2:00 in the morning telling me she did something really bad. When I asked her what she kept going on about how she was "really horny" and how she was "like a crazed dog." I was freaking out and asking what it was. After 20 minutes of no response she texted me again saying "that was it." 

She talked to me once since then and it seems like now there's a formality that was never there before. It's been a week and I'm not sure what to think of it. My best friend has known her longer than I have and is telling me that's the kind of person she is. I have no reason to think my best friend is lying about it either.
<bot>: girlfriend tells me she was really horny last night, tells me nothing happened with anyone and stops talking to me for a week