I have a Best Friend Problem...?

It does not make sense why your BFF is acting that way. It could be a build up of things that led her to behave that way and finally explode. She doesn't want to talk about it so it is best to give her space until if and when she comes around. As long as you know that you didn't do anything bad to her in the past you don't deserve the way she is treating you currently and in those cases its best to stay away from her and her negativity.