Well, this just shows that we can't trust in no one. I know this isn't really helpful but people always have intentions(consciously, I don't know) but what this person did to you was really bad. You must seek the courage to drag yourself together and move on. I hope everything works out for the best.
I'm only half way through but I thought I'd tell you that these two words have run across my mind several times.
You're doing a good thing by writing about it. Write, write, write and you'll see how it shifts and changes. Sometimes it'll be about her and sometimes it'll be about you.
My only words of wisdom would be that you only devote so much time to think about this. Put aside an allotted amount of time and make yourself leave it at that. Do not let this interefere with your life.
I really think you should try to have a no contact policy.
I hope you don't pay her anymore and if you have to, because of a contract or whatever, then the transaction should be done through a third party. She might suddenly be happy to waive the fees.
But honestly, holy shit. I feel for you on all kinds of levels.