Jen there is nothing worse than not knowing why! I too am one of the "I just have to know" people. How can you help fix a problem when you don't even know what the problem is?! It would be driving me crazy too.
I can relate this to my relationship with my mother because everytime I open my mouth I get into trouble. I'm 42 years old and still trying to figure it all out. I know in my heart that there are just some people whom you can not please and that just want drama all the time. If there is none they will create it out of something innocent. The reason I'm sharing this is because I want you to realize that your friend may be the same way. My mother makes friends right and left but she can't keep them because she does this kind of stuff. It's not that the other person really did anything bad but she has the need to create something or blow it way out of proportion just for the sake of excitement.
If you had done something that most of us would think was bad enough to never speak to you again then you would have to know what it was. I think you getting counseling for your depression and how you deal with things like this is a great idea but please remember that this person also has some problems and you can't fix her. It's one of the hardest things to except in life, I think, when you can't fix something.
You keep taking care of yourself and let the rest of this just work itself out. Don't forget that this involves someone else and you can not possibly be the only one to blame. The way she has handled this says she has some serious issues too.
We love ya Jen! Hang tough and keep on being you!