It's been few months I am into PUA, and I do fine now when it comes to meeting girls and closing them. But I want to challenge myself.

So I met this girl before I was into PUA, and she was givning me IOI (now that I think back) and at the same time playing hard to get. Anyway I didn't know about all these and I totally blew it. (I kept asking her out while she kept postponing the dates!)

Now If I meet her in person again I exactly know what to do to win her back. I don't think that's gonna happen...! (And I can't ask her to meet up, since I don't want to appear needy)

I am only in touch with her through Facebook. so what do you think would be best to do. should I neg her on FB? ....

best bet would be to completely cut her out for around 2 months. after 2 months, make contact again (i'd phone her but no more than 5 minutes), see how she's doing and invite her to join you somewhere so you can catch up quickly (because you're busy and you cant be too long).
tease, neg, KINO and dhv.
what also helps is to change your image slightly from how she knew you... so a different haircut or a different style shirt will make you seem slightly unfamiliar to her (helping to pull you out of the zone)