Having run into almost the exact same situation with a young lady who'd been taking careful, measured shots that started out okay, then went to crap, here's what I did.
Suggested returning to the .22 revolver. She didn't like that idea because it had no recoil, and recoil was what she wanted to deal with.
So then I suggested ball and dummy drills. She nixed that plan, too, saying that she didn't like the idea of being tricked and surprised.
The last word caught my ear. Surprised. I asked her about it. She said that at first she'd been concentrating on making the shots and paid no attention to recoil. At some point, however, she started paying more attention to recoil than shooting. That's when accuracy went to crap.
So here's what I did. Loaded two magazines. Told her to point the gun downrange and to fire into the backstop at a quick pace. Not an uncontrolled pace, just a quick one so that she would get used to the gun simply doing its very normal thing. Namely, recoiling. Tossing out brass. Reloading. I wanted her to get used to what recoil felt like. I wanted her to get used to the idea that recoil was normal, unremarkable, and that it wouldn't hurt her.
This was my version of Jeff Cooper's admonition regarding recoil, “Get used to it.”
After a putting a magazine through her pistol, she did, apparently, get used to it. And she found it fun. And she discovered that when she returned to shooting her target, shooting too slowly was almost as unproductive as shooting too quickly: the extra time afforded the shot did not appreciably increase accuracy (already okay), while shooting too quickly often degraded it. In short, she learned to take as much time as she needed to make a shot. Not more. Not less. Just enough. (She was shooting a Ruger P89, by the way.)
Will this work for everyone? Beats me. But it will certainly work for some.