Vampirequeen , It must be dreadful, when someone you know and trusted - and who knew your fragility - lets you down like this.
You do not give details, which is understandable, but whatever she did do you think it is because she is one of those insensitive people, who is completely unaware that betraying confidences or whatever, deeply distresses people? Or did she do it with malice aforethought. If the first, it would explain her subsequent behaviour. If the second her further behaviour is doubly offensive.
I share janerowena's experience. My relationship with my youngest sister was fraught with problems for over 40 years. With the deaths of both parents and younger sister, we have talked more and I discovered the cause of the problems was nothing to do with me. I was being punished because, as a child, she had misinterpreted our parents behaviour to her older sisters compared with her (she is quite a bit younger). I hasten to add we had loving parents who treated us all equally. Our relationship is now much more relaxed, but I am sad that there were such problems in our relationship for so long for reasons that could have been discussed and sorted so long ago.