I'm no majorette, but I'm in colorguard. We do things that are similar to majorette things, like ribbons and such. I would suggest something that's not too slow. She doesn't want to be dragging her routine, but don't do something that's too fast. She doesn't want to be rushing, either. A song that has a moderate tempo, or walking speed is best. My band director calls it andante.
My song suggestions:
"Rolling in the Deep" by Adele
"Tonight I'm loving you" by Enrique Iglesias
"Tonight Tonight" by Hot Chelle Rae
**A few of these songs may have the occasional cuss word in them. If you think about using them, make sure you use the clean version.**