Obviously - this is a very good swing. Can it get better? I think so. Consider the following
The yellow lines represent where the bat could be.
IMO - the wrist movements aren't quite right. IMO the rear wrist is rotating too early in the swing when it should be attempting to control the barrel from sweeping out using more of a hammer like movement. The front wrist should be resisting the rear wrist action by trying to prontate (rotate thumb away from the chest) to keep the barrel above the ball. Her front wrist looks good - but the rear wrist is tossing the barrel out too soon.
It is quite possible that Brooke turns under on this pitch because she was early and bought herself time by making that move - it is hard off of one swing to make a real determination.
But, I think there is a resistance piece missing to this swing that would improve the wrist action. Her current movements lead to the wrist action she uses.
And yes - I understand that her back foot slips on the carpet in this swing. I think the back foot pressure is correct - but her initial movements might be contributing to the foot slipping instead of the foot being able to grip/pressure the ground as long as it is needed.
And before anyone gets upset - I asked Crankermo if he minded - he does not.
I think you are making a good call here Buttermaker. I tend to watch hinge angle but have a slightly different view of it than some others. It looks like your yellow line is added to point out the standard 90 degree hinge. I don't focus as much on the degree of the hinge as the fact that the hinge is maintained. IMO, even if her bat was off the line, but maintained a constant distance from the line at the 'pauses', she would still be maintaining the hinge. That said, it is one swing, and she may be adjusting...