Cheryl, I'm just so sorry that Graycie is so sick. I hope they can get her on a med or meds that will get her feeling better very quickly.
As for Lainey, I don't know of any good books for you to read, but my oldest son went through quite a time when Jordan was dx, so I understand how tough it is on siblings. This is scary enough for adults, so I'm sure it is even harder for a child to deal with.
With Bronson, we just spent a lot of time talking about things that were bothering him. I think it's important to be as honest about things as possible, keeping things age appropriate of course. I would let Lainey take the lead in the conversation by asking her if she wants to talk about the things that are bothering her. Sometimes just talking about it/venting is enough even for a child. You just have to get it out sometimes, you know?
Maybe you can find an activity to take her mind off of things for a little while. The thing that was the hardest for me was to try to keep my emotions in check so that my kids didn't feed off of my fear/stress. This disease is a never ending battle for the entire family, and all we can do is our best.
I'll be keeping your family in my prayers. Please keep us posted.
Stacey