I think there used to be a little gaget called a third hand. I think the often looked like birds with a clamp. That m ight help, but she could use office supply clamps, you know the black ones with the silver attachements I think they are called binder clips or butterfly clips. Whole cloth quilts don't require cutting etc. There is also the accuquilt cutting system. If anyone has access to local schools they often have die cutters that might make some of the shapes. John Flynn has lazer cut fabric for double wedding ring quilts and probably others as well.
I went through a time where I hurt too much to move my arms up. I thought I wouldn't be able to quilt. But I modified what I did, usually machine piecing to hand piecing and could still quilt. I have a little baby block quilt that I think of my victory quilt, because I didn't give up.
My son is a paraplegic and there are lots of modifications that can be made. The therapists have splints or gloves that can help hands that can't do things into shaped things that allow you to function.
I am afraid I don't have that site that I used on this computer. If she is having any therapy her best help would be to explain to her therapist what she wants to do and see if they have ideas. If she belongs to a local bee she might be lucky enough to enlist the help of some of those fine ladies to help her cut out her pieces.