Yours is a really tough question, and it brought back a lot of memories reading it.
2 years ago, right after my daughter's birth, I was diagnosed with cancer. The only relevance is that it taught me who my real friends were and were not. People I thought would be incredibly supportive vanished (ouch, that really hurt), and other people rose from nowhere to really take care of us during that time.
So, to answer your question. I don't know - part of me says let it rest, you have new friends who are genuine. The other part says to at least address it with her and let her know how dear of a friend she's been, how much you've tried to support her, and how hurt you are that she hasn't been available when you've needed it.
I guess, be prepared for the end of the friendship pending her response one way or the other - if you're OK with that, make the best decision for you personally.