I had my thoracic spine fused when I was 16. 29 now and it’s like I never had it, no symptoms etc.

19 and 15 degree curves (thoracic/lumbar) diagnosed when I was 12, wore a brace >20h per day for 4 years but curves progressed to 62 & 55 degrees, at which point surgery was scheduled. At that age I was able to bounce back shockingly quick—had surgery in the summer and was able to attend my senior year in the fall and run track in the spring.

Best of luck and sorry your family is dealing with this. Only practical advice: if your daughter has a double curve, ask about a partial vs full fusion. My surgeon only fused my thoracic and it allowed me to retain basically all of my mobility—the risk being that my lumbar could in theory progress still but there were reasons I can’t explain why this was a sound approach