I believe it is perfectly normal for children to suffer some anxiety and related issues when a parent is diagnosed with a life-changing disease. Children are especially frightened when they lack concrete information and are left to guess how they, themselves, might be impacted. It is NORMAL! My best advice is to help them understand the disease and what can be done about it. There are a number of helpful meds. Most importantly, MS is NOT fatal!!! Again, educate your children! My guess is that you will see their fear/anxiety dissipate quickly once they are armed with accurate info.

My boys were 12 and 14 when I was Dx'd. Just told them the truth...Daddy was Superman and would kick the poop out of this disease, LOL Seriously, honesty and answer questions works well. Good Luck

I was dx before they were born so it was never an issue. I have always had it in their eyes. It has only been in their teens that the have seen me progress/weaken due to MS. But they have taken a larger role in helping me & the family, when I needed and are protective of me a little bit! ;-)
They encourage me and are really supportive of my swimming as they like to see me fighting back.

Both of My kids were raised with Me having MS since they were Little. I, just had them Read about it as they got Older.

I was dx. before either of my boys were born. Not as much info. was available as is now. I was always telling people that I had MS & I still do. My husband & I have always used humor to deal with the 'ugliness' of MS. By the time the boys were in 6 &8 grade (middle school), my symptoms were bad & impacted my life & then it would have been impossible to 'hide'. My oldest son researched MS for a school project. The younger son was always my helper.
I wish you & your daughter well.