To bad you went Zuki, I have a great set for a Yamaha for sale.
As far as what to get for that bike. Depends on a couple things. Is she a small girl who will be growing into the bike for a while? and is she responsible enough to know not to go running thru the sticks, stumps and old fire pits? If she is both get a set of Scat Trak Gliders. They have enough bite to get up anything yet not to much bite where she is robing power.
If she is the kind of kid who will have no issue running around thru the flats and thru fire pits and over sticks and stumps. Find a set of molded tires with the smallest paddle you can find.
Straight or V-cut doesn't make much difference on that kind of machine and the straight ones will get it so she learns to turn with her butt more than the bars and that is a good thing for beginners IMHO.