I also recommend the MS society link that angelac1978 gave you. One of the families I baby-sat for during nursing school
, the father had MS. He was diagnosed in his late 20's, but they didn't tell anyone about it until he was in his 40's when he started showing symptoms (severe limp). He and his wife were very active in the MS society, and he was actually getting experimental drugs and treatments at a local teaching hospital.
I would suggest that the first place your sister start is the MS society, they can point her in the right direction, as well as provide her with a support group which is something she sounds like she really needs right now.
Please remind her that people with MS can go for years living healthy, full, active lives and even though they may have exacerbations there is remission too. Hopefully she will take our advice and contact the MS society so she can start seeing that for herself.
Just keep in mind that right now she is going through the grieving process, and may not be open to contacting the MS society right away. We'll pray for you both over here.