Easy.
Ignore the shit out of her.
the more you do this the sooner she will crave your attention and get back in touch with you.
then you gotta be like 'meh' to her and play hard to get
if it was meant to be it will be if not you're missing out on those that are...
Do it again
You don't.
Give up on your fantasies, man. It wasn't that great. You just don't want to be alone, or you miss the pussy, or you're jealous and don't want anyone else to have her.
WORK ON YOU. Be the man you should be. I know it's a cliche, but it's true. Fix yourself, get on with your life, and your paths may cross again in the future.
Odds are more likely that you'll move on after you're better, and understand that what you're feeling is coming from the inside of you, not her, or anyone else.