I say explain swinging down the correct way and let her hit. While there are some questions, there is also allot to like.
Why? It serves a purpose...yes. But with regard to the issue with the OP of casting....the best way I have found to correct it is by stressing the bottom hand. Get the feel of the pull of the bottom hand instead of the feel of the push of the top hand. Before you go posting 50 .gifs ....try it. It makes sense.
Thanks for the opportunity to clarify. I thought 'hip slot' was a standard reference, but here goes.
Rear upper arm is vertical from a side front view per below.
View attachment 7851
The top hand is not simply "along for the ride". It does have a usage. It is involved with the early working of the barrel. For many the "working of the barrel" leads to the 'slot' ... an "upright vee" at the "RVP Connection Point Position".
The "hand path" of many hitters can be cleaned up immensely by learning top hand/forearm usage.
Short-to, long-through ..... Around, Along ..... work the barrel, throw the barrel .....
How well is she hitting the ball currently?
Do you have any full-speed video you can share? Slo-mo doesn't tell the whole story.
At first glance, I see issues with hand path, weight shift over the rear leg, and extension through contact.
.......................................................................................HAND PIVOT POINT