I think you need to go on an assertiveness course and learn how to stand up for yourself more, or at least to understand that your feelings and needs are just as valid as everyone else's.
Your friend is an emotional leech. She needs to be top of the heap, and she doesn't care how much she hurts you on the way to get there - in fact, she needs to hurt you to get you to leak emotional energy for her to feed on.
She is not a true friend. Any help you ask her for, that she gives, only feeds into her self-aggrandising picture of herself as such an angel, such a helper, such a rescuer. She's doing it for the recognition for herself, not to actually help you because you need it. She really likes it when you ask her to help because it lets her feel superior to you yet again - YOU need HER. SHE is better than you. That's how she feels.
For the sake of your own sanity, cut ties as much as you can. I agree with asking your old boss if there's any way you could do part time work, or even work from home, to try and keep your hand in.
I'm so sorry that your DD is having such issues and hope that the operations etc. that she's had will help her, and help you too.
But lose this witch out of your life if you can - she honestly does nothing actually for you.