Give the kid a chance and get her a 6.5 or a 7 Mauser, or even a gently loaded .270, .308 or .30/06 class cartridge (130 gr TTSXs at 2600 are good deer killers). A 9mm pistol cartridge, even if loaded with 147 gr bullets should be classified as an expert's gun, not a beginner's. The important thing for a kid's gun is a good fit (with a quality recoil pad) to the shooter, combined with light weight and ease of handling for a smaller statured individual. Beyond that, she needs a good trigger and sights she can use, just like everyone else. Then she needs to spend enough time with it to master the fundamentals of marksmanship, before she's put in the field. The kids on our family got .30/06 Husky 1600 series commercial carbines in .30/06, so did my wife, and those rifles loaded with good quality, light weight bullets make a superior hunting rig to a little carbine loaded with pistol ammo. My grandson, unbeknownst to him yet, just got a 7-08 Mauser courtesy of WhyNot . . . who is quickly becoming my primary rifle purveyor.
My grandson shooting Gramma's '06 with 130 gr TTSXs @ 2600. Note the fit of the 12" LOP.
As to this business of shot placement, yes it matters, but in what area of human endeavor, is the novice likely to get it just right? So it is with shooting game. Not only might the shot have to be made under the pressure of very tight time constraints, on a moving target, particularly if the shot occurs at close range. The youngster might well have a greater emotional attachment to the deer than a seasoned adult, then there's the pressure of not wanting to disappoint Dad. Under such circumstances, perfect shot placement might be charitably referred to as unlikely. The chances of a happy outcome go up exponentially if a suitable cartridge is chambered in that rifle.