I know I've read this story multiple times , So I'm not sure why I can't find it.. But heres the summary:

Buffy is in heaven and finds herself watching spike a lot.. She's sees how much he loves her and how much he's suffering because she's gone and she starts to feel sad for him.. Since its not really heaven if you're not happy, she uses her negative emotions to push herself closer to him.. When willow does the spell to bring her back, buffy is already half way there? When she's back to being alive, I think she slaps willow and tells her that she was already trying to find her own way back.. And willow only opened the door for her.
That's all I can remember.. Hopefully someone can help.

I think your looking for learning to fly. I'm not sure of the author, but my phone suggested Spike_spetslayer!!!

Thanks ! Thats definitely the story and author.

http://www.bloodshedverse.com/stories.php?go=read&no=2146&size=&area=2&coloring=


No problem, I found the link now that I'm more awake!
I'm also a bit concerned that my phone is becoming self aware!