Please read up on this thoroughly. It effects people in many ways and strengths.
I was diagnosed with it in 1994. I can't begin to tell you what it was like. I will never fully recover but I have felt better in the last 5 years with lots of sensible exercise and diet.
It's always possible it may come back with a vengance again and completely wipe me out as it did before. It is a long slow recovery process and your grand-daughter will need lots of love and support. I wish her well.