My wife suffered with MS for 36 years before she passed away in September, 2007. From 1996, when she had to quit her job,(nursing) the disease progressed slowly. She fell and broke her leg in 2001 and that set her back immensely.
The last 18 months of her life saw infections, poor circulation, loss of appetite, etc. Sitting in a wheelchair for 10 years began to take its toll on the body. In August 2007, she contracted pancreatitis and had to go into hospital. They were going to insert a feeding tube when she ended up having a respiratory arrest and she ended up in the ICU.
Prior to this last event, we had discussed what would happen if she ended up on a ventilator. She told me very emphatically that she wanted no part of being kept alive in that situation in view of how much suffering she had with her MS. Although it was a difficult decision for me to make, I told the docs to remove the respirator and allow her to peacefully pass away.
I can honestly say I know how you feel and the turmoil you are going through. Your mother has told you that she doesn't want to continue on with all the treatments that will only prolong her suffering. As difficult as it may be for you, I think I would respect her wishes. In the end it wasn't easy for me or other family members but we all knew that it was Marg's wishes and she didn't want to suffer any longer.