Welcome to ThisIsMS, FeelingAlone. My personal opinion is that your thoughts and those of your mother are perfectly reasonable considering the situation she is dealing with.
I do not think that doctors are as all-knowing as they would have us believe. There are new discoveries about the body and disease every day – GI ulcers are known now to be commonly caused by the bacterium, H pylori, and not "stress," as we have been taught for decades. There is question now if cholesterol really causes heart disease – the CRP test for inflammation in the body is a better predictor of heart disease. I think MS will be found to have a totally different cause from autoimmunity.
But until the answer to MS is found, we (people with MS and those who care about us) can only take one day at a time and do the best we can with it. You will be supportive of your mother and cherish the time you have with her.
I personally think that diet is very important in MS (You might find the "Diets" forum interesting here. Or even the story of Dr. Terry Wahls on her website, http://www.TerryWahls.com
MY method of coping with this awful disease is prayer and reading on MS-related articles. But our outcome is not completely in our own hands; may you find the strength you need for your situation. You may "feel" alone, but you are NOT alone – you have found friends here at this website now. We have some very good listeners here any time you need us. All the best to you.