If a BFF hurt you emotionally and stopped being friends then 2 months later wants to be friends again, what do you do?

Be friendly but not necessarily friends.

Wholeheartedly go back to her and become BFF's again. Why did we ever split?

See how it goes, in a couple of weeks you'll see if she's really changed.

Don't trust her, hurt you once shame on her, hurt you twice shame on you.