Need help about a ex gf....?

so my gf of 2 and half years left me 3 months ago for some other guy while overseas and when she got back 1 month ago she told me she loves him. i dont know how she fell out of love with me so fast and into love with him so fast? i did nothing to break her heart and i never cheated she even said i was the best bf and the most loving and caring person she ever knew! i havent talked to her since then and i know i couldnt take her back if she wanted it because of the whole lack of trust. she lied to me about this guy for so long while we were together and now they are in a long distance relationship(different countries long distance) she lied to me for so long about this guy while we were together and about so many other things! need some words to cheer me up as it seems as though there is no possible chance of friendship or reconciliation not on my part but hers. i cant stop replaying everything in my head of what she said the fact that she doesnt love me anymore and wont talk to me at all is depressing as hell.