My son was born with a ptosis. His was not severe, just cosmetic. We had him checked by our pediatrician, eye doctor and opthmalogist and they all said it was not affecting his eyesight. It just made him look sleepy. We went to Dr. James Merritt and he said that the older you wait the better the results are likely to be and he preferred to wait until at least four years old. He came highly recommended and is well-known. He told us up front that it often took more than one surgery to correct. We were pretty pleased, but it did end up taking two surgeries. We waited until he was five and everything went very smoothly. It was day surgery at Children's and my son had no problem with it. After waiting a year, I still felt his eyelid was droopy and the doctor agreed, so we did the surgery again when he was eight. Again it was day surgery at Children's and my son took it like a pro. His eyelid looked a little bad for about a week or so but it healed quickly. I kept him home from school for a few days, but he felt fine. I was just anxious about him getting it hurt.
His eyes look great now for the most part. I have noticed that when he is looking down (like when reading) that the eye that was fixed is actually open more than his other eye. Kind of creepy looking, but most people would never notice it. From what I have researched, it is very difficult to get them just perfect, but if you look at most people, their eyes are not identical. Almost everyone has some slight ptosis that increases with age.
I would be a little concerned about it being done so early. Perhaps hers is more severe than my son's. He had no vision problems at all. I just hated that I had no decent pictures of him for the first eight years of his life, because the ptosis always showed up more in a photograph. I learned to try to take his picture in a profile or a three quarter view with his bad eye away from the camera.
The good thing about surgery on young children, is they seem to recover very quickly and have no anxiety. My other son had hand surgery when he was only 11 months old and he went through it very easily. The scariest thing is having the anesthesia. You just never know how they will react. Luckily, both of my kids did great.