PLEASE have her shoot one first !!!!
I suspect she'll change her mind.
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Agree.
I think that is a touch too small. Unless she has really small hands and is able to get her pinky fully on the grip it is going to be uncomfortable to shoot.
You can get away with the hanging pinky on something like a glock 26, because it so fat, and easy to hang on too. The Kahrs are thin (which is awesome), but the extra 0.5" you gain in height going from the PM9 to the P9 or CW 9 makes quite a difference.
If you can't find a place to rent them to you, perhaps the store will let her hold it while you slap the muzzle to reasonably recreate muzzle flip/recoil. It's not exact, but at least it will let her see if there are any spots that are prone to rubbing and chafing her hand.
If that's the biggest gun she is willing to go for, than by all means go for it. It is certainly a servicable firearm, in a potent caliber.
You might find it to just might be a tad on the short side grip length wise.