I do think it's pretty odd that she didn't seem to hear the "I'm going to Europe, goodbye" part. Other than that, it's just what you expect from a chick who's been treated in the way she thought she was being treated.
She thought the guy had just ended the relationship without even bothering to tell her. It's not surprising she got a little bit angry, then flipped out, then slept with some other dude on the rebound.
And no, Micro, she didn't "immediately" freak out. If she goes off the deep end after two days without any contact from her boyfriend, we can probably assume they talked more often than that. She had his Mom's number, so I'm also going to guess the relationship was fairly settled, hence pretty important to her. Then he "refuses" (in her mind) to answer any calls or emails for two or three days? That would be a pretty big issue for most girls, I should think. Maybe you're more accustomed to a long-distance relationship, where a few days without contact would not be unusual. Or maybe it's just because (in my only romantic relationship) we are neither of us happy unless we see each other every day, and perhaps that colors my view of things.
As for the email with all the misspellings, well, she was drunk. Who'd a thunk?