MS daughter, people may recommend alternative therapies, vitamins, diet, or exercise but what is likely the issue is depression brought on by dealing with a diagnosis that has no cure, and a bleak outlook. I sank into a deep depression after my diagnosis in 2012. I had basically convinced myself i wouldn't be walking within 5 years, and would be bedridden within 10. Ultimately becoming a burden to my young family and die of an infection from bedsores. After feeling sorry for myself for long enough I faced the fact that I am the primary provider for my wife and sons now 2 and 4 and that I could not afford to let this happen. I had a responsibility to provide for my family and stay as healthy as possible for as long as possible.
Your mom may feel she does not have this reason, a purpose to explore all possibilities to treat this illness. You and your sister are grown up, moving out, and don't need her anymore, she has obviously worked a long hard life as a nurse. Giving up is easy, and if she is a nurse she probably hasn't seen a lot of easy. But has seen the worst of every disease.
My recommendation is you remind her she is still needed. Your family will not function the same without her taking charge, her opinion matters, whatever it takes to get her to realize she has value. Give her something to look forward to, help her adopt a regimen, any regimen that will give her back some control. Show her examples of people with MS where it is a minor inconvenience and not impacted life or happiness. I applaud you for trying and wish you the best of luck.http://intelligentguidetoms.wordpress.com/