I find it funny when a player parent say they can't hit slow pitching. Truth is they can't hit the fastest 5% either (not many can, and you don't see them often).
So the reality is that they can hit average pitching. As a coach I tell them they have a mechanical issue they need to sort out. Nine times out of ten they don't understanding timing and how to resist.
Just my observation.
There's no doubt something mechanical is going on. I didn't make this post to brag, I made it to try to find out why she isn't hitting the slower pitching. To me, it looks like she's overanxious and tries to "kill" it which results in dropping her hands a little. However, when the ball starts moving some, that doesn't seem to happen.
No one is hitting the fastest 5%, like you said, but that's part of the reason why, at the lower age levels, this game is dominated by good pitching. That's why the game we played against the good pitching was 2-1 why the other games were 16-0 and 11-5.
Good pitching beats good hitting. Same is true in baseball and softball.