Hey, she uses the same DM Screen I do! And she's got the perfect height to do the evil DMing. Cuts off the grinning when PCs do something that they shouldn't have.
Her DMing skills are good, VERY good for a 12-year old.
She ran us through Dungeon of the Fire Opal (which had an invisible badguy - the ultimate challenge for a first-time DM on her first game), as well as the original White Plume Mountain (although I wrote the 3e skill checks and timing required to cross the hot mud geisers room).