Sadly, what happens is the relate-ability factor that you two once shared together has changed, and that may inevitably cause distance to grow between you both. Her daily life and your daily life are so different, your life's perception is altogether different. The real difference is, you can relate to her life, because you once HAD that life yourself....so you "get" her. She, on the other hand, cannot relate to your daily life (even though you tell her, she still can't truly imagine)..... which may unconsciously make her feel uncomfortable. She doesn't "get" you. Make sense?
Nonetheless, she could simply be going through a busy time in her life, and you may be taking her distance too personally (you are probably very emotional right now with the big, recent changes in your own life). Perhaps she is exhausted, depressed herself, or really is avoiding you because she may feel guilty because she still has her health and career and feels she doesn't want to be a reminder of the person to you of the person you used to be. Give a little time, and write her a letter (as suggested by the person preceeding me). From my own experiences, I have also lost good friends..... a lot of it is due to strained finances. With not working (and medical bills out the wazoo), nobody is calling to invite me to do anything or go anywhere because 1.) they know I can't afford it and 2.) I may be having a bad "pain" day and cannot do all the walking involved.
Good luck and hang in there. Hopefully you will get the answers you need soon

Vanna