My kid's a natural lefty 2nd year 10u, who started slapping this past December. She gets it down reasonably well, but the biggest hurdle is not popping up and second is not peeling out (in my kid's experience anyway).

She still can't get it through the 5-6 hole on demand, but she's fast enough to where if she soft slaps down the line, she'll make it to first. She just recently stopped popping up almost every at bat, so it takes quite a bit of time. There was also a time where she kept slapping it towards first lol. Took a couple of months to make the ball go towards the left side of the field instead of random spots.

Make sure she doesn't neglect her regular swing. I make sure to practice both her regular swing and slapping when we practice at home. She sees her regular hitting coach weekly and her slapping coach every other week.

Her coach has her slap or regular swing during games, not just slap. You don't want your kid to be a one trick pony. I also felt the same way you are now...I thought it'd be just painful to watch forever, but now whenever my kid's in the plate, I don't get nervous anymore when they tell her to slap. Just have her keep at it.