Your daughter sounds a lot like me. I have quad CP, but my right side is more affected. My right foot is 1 1/2 sizes smaller, it turns in more than the left, and I can't really move it due to spasticity in the ankle... plus I had a SPLATT and a few other things done on that foot back in the day.
I had bilateral hamstring lengthening at 13 (7 years ago). It was a REALLY easy surgey, besides being half covered in plaster in the middle of summer! I would probably do it again if I had the choice to do things over, but I might have waited a few years. I know if I hadn't had it done I probably wouldn't be able to walk right now, but I lost so much strength after the surgery that never returned, and that really sucked. I used to be able to skateboard and surf a little, and I definitely can't do that anymore. I've also not ridden a bike since a few months after my surgery, but that is partly because I got into a nasty accident during PT. I could probably still ride if I tried.
I think I'm just generally slower, less coordinated and not as strong after the surgery, but keep in mind this doesn't happen to everyone!
Some positives are that I can straighten my legs completely, even though they have started to contract again. I couldn't straighten them before. Also, my walk is a lot smoother except for a slight increase in the contorsion of my right femur. Furthermore, once I got used to my new set of legs so to speak, I started falling a LOT less. Pre surgery I probably fell anywhere from 5-10 times a day. Post surgery was hard to deal with being so loose, but now I don't even fall every day!
Long story short- I still would have done it, I just wish someone had told me about the possibility of weakness instead of everyone (parents and doctors) making it sound like it would be some magic bullet cure all for my problems.