Kelly, I'm so very sorry for this news. Of course you're scared. Who wouldn't be? But please, don't give up hope.
It may be time to give some hard thought about ending contact with your mother. Hops is right. Don't let her own you any more. The sad reality of an N with money, is that they won't help a child in need, unless it is the GC. If I were sick and/or dying, my mother wouldn't give me a dime, and worse, would rub it in my face and tell me it was my punishment for being a bad daughter.
The stress of dealing with your NM is going to make recovery harder for you. Stress is your body's worst enemy. If your mother can't be there to support you, either emotionally or financially, let go of her. If it turns out that you have precious time left, spend that time with peace and happiness. Don't let her take that from you.
I'm writing this as I watch my N mother (who has terminal cancer), mistreating my 48-year-old sister, who has advanced breast cancer, and may not survive. NM is jealous that her daughter's cancer is taking attention away from hers. Instead of loving and caring for her daughter, she's attacking her for usurping her own cancer and impending death. That's how these people think. The only way to find peace is to let go of them.
Just please, get rid of that stress. Stress is a killer. Stress makes cancer worse. You need to be at peace with your mind and body in order to recover. Please, please take care of your emotional health as well as the physical.
You are in my thoughts as you go through this difficult time. Thinking of you, and sending you me absolute best thoughts and wishes . . .
Kathy