So sorry to hear!

Some tips on the vision--does she wear glasses? (If not, consider getting a cheap pair of plain glass (no prescription) ones.) I have had terrible troubles with double vision, and constantly changing and irregular causes, which seemed to be constantly defeating my ophthalmologist's efforts to control. So, we finally came up with just some simple tricks.

One way to stop double vision caused by the eye muscles not coordinating the eyes, is to cover one eye. But an eye patch looks terrible, and can be very uncomfortable. Especially for a kid.

This is why you need glasses. Cover one lens with scotch tape, the opaque (whitish) kind, not the shiny clear. This blocks the vision in one eye, without blacking it out completely. The cloudy effect of the tape fuzzes out the vision enough that only one eye will take the job of seeing, yet she will still have peripheral vision around the lens (helps with not bumping in to people and things around you), and light coming in (versus the black of an eye patch).

For me, one whole lens fuzzed still played games with my head, as it was my dominant eye that was wandering the most and needed fuzzing out. So, we cut it back to only taping one half of the lens, from just about the center line to the outside of the glasses. This way, when the eye is seeing straight, I have both eyes working, but if it wanders outward, it goes into the fuzzy part and stops contributing to what I see, so there's no double vision.

If her eyes wander inward instead of outward, try taping the inner part of the lens.

As my eyes change the severity and amount of wander, at times I've been able to reduce it to just a strip of tape about 1/3 of the lens, again just past the center mark so I get straight vision, and at other times the entire outer half needs covering.

It's a cheap easy trick, if she doesn't wear glasses go get a cheap pair from the dollar store, even cheap sunglasses and take the lenses out, then just wrap one side in scotch tape, just to test if it works for her.

Also, instead of just an optometrist, she should be seeing a good pediatric ophthalmologist with experience in eye muscle disorders, if she isn't already. A pediatric ophthalmologist is better as a growing child has other considerations for them to watch as well.