That sucks big time .
Although i’d have confronted her as soon as I noticed something was a little bit wierd. There’s no need to be aggressive or anything, but it would only help you to insist and be authorative about your own affairs. I still think she’s a jerk for not having the guts to tell you face to face. I mean, come on, breaking up by email shows a weak character.
But still, life goes on, and I’m sure there will be many more episodes of the sort, some worse, some milder. Relationships are a very touchy subject, some happen for fun, some for company, some for a soulmate (possibly love), some even for revenge. You just have to use both your mind and your heart, until you find your match. If i’m not mistaken, you’re still young, so don’t give it to much thought.
Good luck in future relationships, but be warned there will as many heart aches and tears as there will be fun and excitement.