If the stock fits her and it isn't chrome plated, why bother doing anything at all?
Now, if it's a shiny urethane finish, a $2 can of flat-brown spray paint would work just fine to get a dull finish. Try Big Lots or Dollar General.
Camo doesn't do squat for deer hunting. Any dull finish is just fine, whether gear or clothing. Being still and not moving is even more important...
Art