In my opinion at that age she should work on perfecting a changup and dropball before she starts working with other grips especially ones moving side to side. A mens pitcher i used to work with that travelled around the world playing told me that pitches that move side to side only are useless...
Palm down seems to be way better to me. i do play mens fastpitch so the speed is basically there with any grip enough to make it do something but when i first started learning to make my pitches move i threw a curve almost every pitch just at different speeds. palm up is about 5mph slower then...