Interesting observations - I think they make sense.
Like your daughter, my kids are 'stuck with me' in between lessons (they see their teacher for 40 minutes once a week, and practice at home 20-30 minutes 4-5 times a week).
The situation reminds me a bit of the quandary I faced years ago when they started having homework: would it benefit them more if I just made sure they spent time on it at home, and let them find out in class that they'd gotten some of it wrong, or if I went over it with them and made them rework problems they didn't 'get'?
I opted for the latter approach, except for the few times when they told me either that the teacher asked that parents not help, or that they preferred to check their work in class.
The reason for my choice is that I think with both homework and music practice, there's some benefit to catching errors early, before they become ingrained habits and have to be actively unlearned.
I've been pulling back from that approach, though, as ds (now in 7th) has gotten older and more self-sufficient. I no longer check that he has done his homework, much less check it for errors. He asks me to quiz him before exams, and what I hear and see then indicates that he's doing a great job without daily oversight by me. (Dd9, in 4th, still needs the oversight.)
To get back to music: I don't know how long either kid will want to continue with it, since each has another extracurricular he/she seems to prefer; but if they study long enough, they may well reach the same level of independence in that area too.
