I agree with everyone about how you have done what you can by asking for forgiveness. You did go the extra mile.
I have found friends I did not know were "there" when I was well. And the friends I thought were- really aren't!
In the end, I just do what I can. I focus on myself (hurray for selfishness) and my family. My true friends understand.
I think that had it not been cancer, it would have been something else to divide your relationship with her. Move on.

Friendship should not be treated as a sideroad weed. Even the weeds need water !!! She used Roundup.

stay well,
maria