I lost all of my friends at once over a stupid misunderstanding: My friends accused me of being gay (Because I didn't have a girlfriend) and drug me up to the high school's rooftop and proceeded to beat the sh*t out of me till I nearly fell unconscious and one of them started to strangle me to finish me off. I gathered all my remaining strength and threw him off the roof and promptly passed out. I have never talked to them since and never understood they're sudden immediate need to try and kill me. I've had a hard time making real world friends since that incident. I don't feel like I can trust anyone but I've managed to make a few friends since then. If I can make a couple friends after having everyone I know try and kill me, you can make up with a friend you got angry at.
So... Agoraphobia? Maybe talk to someone about it, do you have any family members who could help you? I've locked myself up in my own house for weeks at a time just because I don't want to interact with the world or I'm in a video game worm hole. Perhaps you could go out with a friend / family member and go to a quite place and slowly acclimatize yourself to the outside world?
Jesus, duder. That's really one of the worst things I've ever heard. Sorry you had to go though that, but I'm glad you've made new friends since.
As for the OP: It seems like a very complicated situation you're in, but if it's a friendship you really care about, all you can do is explain yourself, apologize, and hope she understands. I don't really understand how she doesn't sympathize with your condition if you used to be best friends, but perhaps things are more complicated.
I've had a friendship come back around after a solid chunk of time away from the person, so don't give up hope!