What would you do? , ok so I've been dating this girl and i've loved her for the longest time ever.. ?

And she "Loves" me too, I left about 2 months ago (Personal problem) and the only contact i had with her was email. Last week she e-mails me saying that sense i haven't been around shes been feeling lonely and said she met this other guy that she is growing feelings for .... Then she says that she is going to go out with him but she still wants me. So basically she wants me to wait here like a idiot watching this dude date my girl until they break up =( .. I was upset so I told her that it's over but she got all sad so I was like " nvm it's not over " .. But I'm ever sadder because she is with someone else .. What should I do =(? Should i call if off?