She's doing great! She's a keeper
Have her glue her trailing elbow to her ribs.
She could sit/squat a bit more on heelside
Have her let the board run...instead of swishing her back foot. Swishing the back foot kind of finishes the turn too early. In part that's why in the creepy vid...the focus is on the front/leading side of the body...and in general you just let the front knee, hip and shoulder lead...and since your body is aligned, in the cereal box, the trailing part of your body will just follow....and you don't need to over-rotate and end up swishing. But you let the board run and use the sidecut of the board...instead of your body...and thus it becomes more efficient riding because you are using the designed sidecut to do the work.
The main thing is...she is not attacking the nose. You can see that she is not getting on that front knee and really bending/driving it. And that as a result...abit later in the turn (at the finish) she is overcompensating on the trailing leg by swishing it....which you also see that she is bending the rear knee more than her front knee.
another thing that might help is for her to get her leading shoulder in the game...she has pretty good form, i.e., stacking and alignment...but she is not attacking the initiation of the turns...which will involve becoming a bit more dynamic in the phases of the turn. That is, going down on the initiation, squatting in the middle and rising up on the finish of the turns. She looks abit hesitant and is not weighting the nose...and is kind of in the middle to slightly too far in the back seat....get her to shift her leading hip (and shoulder) sideways toward the nose...while also driving/bending that front knee (toeside). And for heelside...getting on the nose, swinging the front knee towards the nose and get her hip and leading shoulder also in the rotation towards heelside....then squatting more in the middle of the heelside turn.
anyway my long-winded armchair 2 cents