With my older ds, he would respond well to being given a "job" to help in the situation. Something to help and be involved and be needed, but not too critical. He is very sensitive and I can only imagine how devastated he would be if his little brother got a T1 dx along with all of the roller coaster that goes along with getting it under control. I don't know if it would help your dd but with ds something like having the job of getting yds a drink of water when something critical is going on would be a perfect little responsibility for him.
I can only imagine how helpless your dd is feeling, perhaps having an important way to contribute and help would help her.
Hugs to you.
