To answer your question directly, it sounds perfectly fine for her to use a PPK in place of her Taurus, if she is comfortable with and able to control it. She would have to train very hard to learn to shoot well with her non-dominant hand.
Now, the rest of the answer
- has she fired the PPK and compared it to her 9 mm? She may find the recoil of the blowback .380 more difficult to control (snappy) than a locked breech 9 mm, not less.