To help you answer...
Is there the danger as she ages that this will cause excessive wear-and-tear on her feet, knees, and hip joints? Will it affect her back? My legs were not "right" and I lived with pain, although it was "normal" to me. But by 16 I had some osteoarthritis. Things just get slowly worse over time. I dream of no pain. A pharmaceutical company came out with a medication that would give people like me what I want and the FDA did not approve it because people then used their joints a lot and wore them out sooner. I just wish every one on that panel could live with the pain, then see whether or not they'd approve it. It works, but they don't trust us to go easy on our joints.
On the other hand, will the surgery truly fix her and prevent the arthritis, or will it just cause other problems?
Oh, and by the way... I COMPLETELY know the scream that must be inside you because the pediatrician essentially DID THIS to your daughter by not listening to you to begin with. It would have been so simple to just refer your baby to a pediatric orthopedist to check. The doctors act like the referrals or running tests are money coming out of their own pockets! Medical insurance does put pressure on them to "keep down costs." And that is done at our (health) expense.
I have my own regrets with my own baby who is now an adult... I had the scream stuck inside me, and am turning it into advocacy (http://www.ItsNotMental.com)
UPDATE: Then, with that new information you just provided, YES! It is so much easier to heal at 6 than in her 40s. And while young YOU can take care of her. She won't be missing work, or having children of her own at home to care for.... As long as the surgery won't cause a DIFFERENT set of problems such as to her pelvis.