how to get a girl to like you, again?

So Ive.had a thing with this girl for a while, and everything was going great, I was about to finally make.it official, then she tells me out of the blue really surprisingly that she doesnt feel the same way about me, i find it hard to believe cuz a couple days ago everything was going so well. Anyways I miss her like crazy and its been a while since ive even talked to her (once but it was awk small talk) but ive heard from her friends that she kinda misses me, I just dont know what to do