Dream Chaser, I want to welcome you to the forum, and also offer my condolences on the loss of your father. I'm sure it must be very, very difficult to now be dealing with a mother who is so ill. Everyone is different, so nobody can say for sure how long she has left. You might try pinning a doctor down as to whether an educated guess would give her 6 mos. or less. If this is the case, you can get Hospice involved. Some have nurses come to the house and some have actual residences where the terminally ill can stay. The fact that the doctors have placed no restrictions on her is an indication that they think she is terminal.
When I was diagnosed with liver cancer, I asked a liver surgeon/hepatologist how much time I had left. He didn't want to answer, but I told him to just give me an educated guess. He said, "Six months, without treatment." That was enough info for me to know I needed to have something done. I underwent available treatments and surgery and am here over a year later, still cancer free at 65.