Sending you strength and sending your daughter healing thoughts.
It's not the same operation, but similar emotions: my stepdaughter had scoliosis and had an extendable rod inserted. It was lengthened a few times as she grew, but eventually, after it broke, they decided to put in the permanent rod. They judged her physical age based on x-rays of her hand which determined she had very little growth left in her future, so a fusion made sense. She might be a tad short-waisted, but no so anyone has ever noticed. Lots of people are like that just naturally. Think of Michelle Obama or Robin Roberts - long long legs, shorter torso (by comparison) - and they are both gorgeous.
You've done what you can do - several appointments and opinions, and you're going to alleviate her pain which is really important after this long a period of time. Hope it goes well and that she has a speedy recovery.