I have just experienced the same thing Frodo...
I loved my girl and she loved me back. We had been together for like 1,5years. One day she got this free training lesson flyer from a gym close to home. She was thinking of not going, and i was like pushing her to it. I said it could be good for her cuz i love to train. Well, she listened to me and went. She liked it and signed up at the gym and started training regulary. 3 weeks after the first training lesson she told me that she hadn't got the same feelings for me any longer and it would be wrong to continue. This came like lightning from clear sky. 1 week earlier we had just been laying in bed and she told me that she would have given up life if she hadn't had me (she has experienced alot of family problems, which i helped her through). But suddenly everything we had said and done together didn't matter any more. I tried to make her come to senses, but she had made her mind. I packed my things and moved home to my parents totally heartbroken. Some days later I found out she was dating the training instructor. Yeahyy, great!! F**** *****!!! Absolutly incredible.
What saved me from hell wore all my good friends. They backed me up, gave me "The game" and now 1 month after breakup Im starting to see the light. There are lots of great women out there. If it wasn't ment to be it simply wasn't... But take your time to get over her, new women may not be the answer...
As many others has said before me, you will get over this Frodo. You have probably learned alot. Before you know it you will look back and laugh about it all, and understand you got the better half of the deal than her. She lost something, you didn't!
"What doesn't kill you makes you stronger"
(sorry my bad english)