Tad, I agree w/uR that maybe your mom is holding on for some reason. Your mom has fought a long, hard battle w/cancer and she's been strong throughout her ordeal. When God is ready for her, he will call her home. From what you posted, it doesn't sound like it will be much longer. Spend as much time as you can w/her and let her know it's okay to let go and that you will be okay.
I'm very sorry and pray that God will end her suffering sooner than later. My thoughts and prayers are w/you and your family.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.