Like many young hitters,her hands arms torso are starting to swing (move forward) well before she gets her foot down, I like the Go Drill but not fond of back knee turning towards the catcher part. Even if it does turn very slightly towards the catcher, I would not say that. I would rather have them feel as if the knee is stable and the back hip rotates (loads) away from plate. I like the Justin Stone video, too. https://www.youtube.com/watch?v=vLbpAoG_dgQ
How to fix? I'm ecstatic she gets any separation during the stride. Do you have a drill for this?
When my DD first started she dropped her hands as well and I had her hit off a high tee, about shoulder height (I put the tee on a bucket).
Whether or not this helped I am not sure, but she stopped doing it eventually. At the end of the day your DD needs to get a feel for turning the barrel nearer to her shoulder.
It will take some time and my DD still has some bat path issues.
Tewks has good stuff mostly but if you watch that Go drill without having a deeper understanding of things he's NOT showing then basically what he is showing there is falling off the barstool/losing the coil, NOT forward by coil, which is what that drill should promote.
So to the original poster, I'd dig a little deeper with your DD...her stride issues are a symptom of other problems that others have pointed out such as lack of coil/riding rear leg and a drop and sweep arm swing. Given where she's at now, her current success and her age SHE is ready to learn a better swing not just apply a bandaid. If you've got the time, start digging in. Find the thread where Eric F has documented the progression of his DD and search some of the terms that people have thrown around here (turn the barrel, forward by coil, DBSF) and dig into some of those threads. It will be worth it.