I’m at a loss... help !

[PDM]

Going to be a bit blunt here...

You took something she liked, and turned it over to an abusive J**k@*@ coach and justified it because of 'tough love' and 'mentally strong' which is leading her to hate even doing this anymore.

Why would you do that? Why would you let it continue?

Let me guess - he has some rep of building pitchers or 'knowing the game'

She isn't having fun; you made it a job with an abusive boss. Before you try to fix anything mecahnical, stop these lessons with this coach, find a better fit and hope the damage isn't permanent.

It is still meant to fun and enjoyable.

Excellent answer! I would add that the parent seems to be taking this way too seriously. That also puts pressure on the player that she doesn't need.