Just because she is short does not mean you need a smaller stock.
What determines proper stock length is the length of her upper arm and forearm.

Also remember that a lighter rifle generally has more felt recoil.

Cutting some length off the butt reduces the length of pull. Do it carefully so the cut is true, and then fit a grind-to-fit recoil pad like a Kick-Eeze or Decelerator.

Have you looked for youth stocks? That might work for you with no modification.