I know how you feel, sweetie -- I really do. But a 20 year friendship is too precious to throw away!
There is a saying that goes like this: "Resentment is the poison I take to kill you." And it's true. When you carry resentment and hate around like this, all you do is hurt YOURSELF -- you don't hurt the person you're resenting. You eat yourself inside out. It's like cancer.
Yes, what she did was crummy. But some people are more selfish than others and they just don't KNOW it.

She didn't know she was hurting you and she STILL doesn't. I suppose that BECAUSE you've been friends so long, she expects you to do all these things for her, and that's where she's wrong!!! You should never expect or assume ANYONE will do ANYTHING for you, without your asking -- and even then you shouldn't ask them to go out of their way for anything!!!
I don't know if you want to forgive her or not, but as I said -- to throw away a 20 year friendship is a tragedy. Friends are very HARD to come by, especially friends that you can trust. Perhaps the two of you could sit down and have a long talk, and work this out. Have a heart-to-heart conversation, and let her know how this all hurt you -- and see what she says. If then she apologizes, perhaps you can forgive her. If she gets MAD, then perhaps the friendship isn't worth it afterall.
I wish you the very best. But please give this a chance, and don't carry this hate around. God bless and please take care. Hugs, Lee