So sorry, but your 'friend' sounds like a total waste of space. The fact that she fell out with you 16 or more years ago and never wanted to put it right until, maybe, she'd exhausted the patience of many others should be a big clue. Her life is obviously a mess and you were useful to have around, just to listen to her complaining and pick up after her. You really shouldn't be surprised at how this was going to end - again.
She sounds totally self-centred and selfish, wrapped up in a life which is out of control. She's made it clear that she's not interested in you or your health problems or helping you in any way.
So switch off, break contact and give it up, you're worth so much more. Hopefully you can stay with or near to your StepMum, where your visit will be really welcome; and I hope that you get the help and support you need from real friends and family and that your hospital news will be less worrying for you when clarified. Please concentrate on caring for yourself, focus on positive things so that you can get through this episode and put this person from your past out of your mind completely.
And don't feel hurt or shocked - she will have done this to others.
I hope you will soon have a clean bill of health, but in the meantime turn your attention to yourself and refuse to waste any more time on worthless people. Try not to worry - good luck.