Is this the beginning of the end?

My mother's cancer has been a total roller-coaster in recent months and may be coming to an end. The day before rads for debilitating low back pain she fractured her femur simply by standing up. Since her condo was on the 3rd floor of a walk-up building, she had to sell her condo and was never able to go home after the ambulance got her. After rads they suggested surgery to have a rod put in her leg so that she could avoid 6-8 weeks of rest and rehab and start walking right away. During the surgery they found the damage to the bone was more extensive than what was seen on the scans so while they were able to get the rod in, it wasn't as stable as they'd hoped so she still needed weeks of rest and rehab. During her final days in rehab she began to get very fatigued and have issues with hearing and vision which were put off to steroid withdrawal. She came to stay with us and the plan was to stay until we found her a place with no stairs. She has gotten weaker and weaker and last week they found her potassium was dangerously low so she was put on regular potassium. Within a couple of days she seemed more alert and was getting her appetite and energy back. Monday morning she went in for Faslodex and a blood transfusion. While there she received more potassium as well as magnesium. Then while trying to get up from the bed in the treatment room, she fractured her arm and opposite collarbone. Since she was using a walker to get around because of her femur surgery, she is now unable to move around by herself and is back in hospital and will be sent to a rehab facility for at least 6 weeks until she is able to move again. She has almost completely lost hearing and spends most of the day asleep and has insomnia at night. Her last scans still showed cancer only in the bones with no organ involvement. Last week the oncologist told us that she would continue with Faslodex for one more month to give it enough time to work and hopefully give her body a chance to get stronger since the only other options left are chemo and is she doesn't get strong enough then there will be no more treatment.

I don't understand how this is happening so fast, especially given that she has a "slow-growing" cancer and had a relatively good prognosis since it was only in the bones. I understand that low potassium and magnesium, as well as withdrawal from Decadron could cause weakness and fatigue and even hearing and vision problems, but she just seems to be going downhill so fast. Has anyone experienced such debilitating symptoms and bounced back? I can only assume that the cancer has spread elsewhere since her last scan.