^^^^Agree with most of that.
The only change I would suggest has to do with the nature of these kinds of flexibility problems. Usually when you have some really tight parts. and like IK said, she sounds on the upper extreme of that, you tend to have some really overactive parts and some weak parts opposite that. In other words flexibility imbalances come with strength imbalances. Matter of fact the leaning forward can have a lot to do with that and not JUST flexibility. They go hand in hand.
Something that I disagree with most people on is the idea that the squat is always the best. Many think that once you can achieve the squat that the body will somehow magically overcome any imbalances and you will work up to your full potential. But that isn't really the case. What will most liklely happen in a case like this is once the flexibility issues have eased and a full squat can be realized some very good initial progress will be made but then a premature wall will be hit.
When I say premature I mean premature relative to individual potential. The other problem is that I would be concerned about some overuse injuries that might crop up with that progress.
My advice is simple. Do the Rippetoe however but have her do lunges with dumbells. There are techique caveats on that as well which we could get into. I would start her with "static split squats" until balance is better then move her to reverse lugnes and then probably to regular dynamic lunges. Along with some specific core strengthening stuff. Once she's progressed well with these for a while going on to the squat will be both more productive in the long term and less likely to result in injuries.
Edit* This is NOT one of those lunges for girls things. I would have given this advice to anyone with similar presentations. Frankly I do lots of single leg variations and many of the "squats only" guys coulnd't handle it. They'd be passing out on the floor trying to catch their breath while cursing my name
