I am a firm believer in having choices in this life. Obligation only goes so far with me (sounds terrible I know) but even if she was the nicest person EVER and still grated on my last nerve I, which has happened, I would exercise my right to not feel like I had to do anything at all.
Personally I think the party should be for you.Survivng leukemia, now that is something to celebrate,congratulations and forget the party she doesn't deserve it.