Have you showed her video? Does she do this during her tee work? and how much tee work is she doing?
So, is she hitting to RF or not hitting at all?
Is she trying to imitate a MLB player?
One of the things that is good about T work is that you can set the height of the tee high and have her hit that way for a while. This will help eliminate some of that drop.
The other thing I have done and this is really pretty effective but not conventional is I take a strip of towel and tie in into a loop. I then have the batter place it over their neck and I have them put the front arm through it like a sling.
I hand the batter the bat, place a ball on the tee and tell them to take a swing. It wont take long for them to figure out they are not dropping the hands with that sling around their neck.
The other aspect of that is if they have a tendency to take the hands to the ball it stops that too. The only way they are going to hit the ball is to rotate the hips, core, and shoulders to the tee.
Do not do this for long periods of time. Maybe 10 - 15 swings and start SLOWLY at first then speed up. Over the course of time you will see improvement.
PS: Also focus on not letting the her drop the back elbow down to the side immediately. I would bet if she is dropping the hands the elbow is the first move then the hands. The elbow needs to come around the corner away from the body into what some term "The Slot".
Hope this helps. Keep me posted.
I would really want to see video before I'd remove that hand lowering. It could be that the hand lowering is excellent....a loading technique....and that she needs to do something else better.
Ummm....My DD used to do this, and trust me, when she started seeing faster pitching, it was far from excellent. If it was a good idea, you would see a lot of college girls, team USA girls, etc. doing it, and I don't recall seeing that.
Hitting with a high tee (I set mine on my ball bucket, so the ball was right at her arm pits) helped my DD.