Ah, so sorry to hear about your mom! That's a tough blow to take, especially since she passed away so quickly (in cancer "time"). My grandma had cancer and somehow she lived with it for 7 more years, but it was tough, especially on my mom (I was mostly away in school).
Yeah, you're better off without your so-called friend. It's hard to have to deal with something terrible in your life and with the disappointment of seeing the way she vanished from your life when you needed her. There are people like her. The good times kind of friends. Totally unreliable when you need them in hard times.
And I'm sorry for your grandma. My mom had pancreatic cancer, which has one of the lowest survival rate, if not the lowest.
Yeah, you know the saying about good friends. It was a good lesson for me and I'm glad I don't have to see her again. Italians say meglio perdere che trovare. Which means better to lose her than to find her.