I am so sorry for your loss... Losing a loved one hurts so much. You have my very deepest condolences. She's gone now though, finally at peace. It hurts to think of all the things you might have done.
I know--I did the same for my mom. But I believe you did the best you could with what you knew. So do try to be kind to yourself through all this. I know how hard it can be not to feel somehow responsible.