Re: Youth rifle (and maybe book) suggestions
Deer, maybe javelina and hogs (I'll keep her on little pigs) and who knows; could be some yotes or p-dogs. (but for the latter two I can put her prone with my Varminter)
When it comes time for her to hunt elk (or a true muley buck hunt) I think she will be MUCH bigger, it is just a much harder hunt in my experience. The TX whitetail would likely be out of a stand and the doe hunts here would likely not be more than a couple hundred yard hike from the truck.
When it is time to step up to a larger caliber, it will probably be time to step up to a larger gun. I have no problem buying her a 7mag or .30 of some flavor in a few years, it's part of the fun!
I am certainly not trying to find her a "do-all" type gun, if I were that guy I wouldn't have a safe full of guns. Finding different guns for different tasks is part and parcel to this hobby.