...Ok, apparently SPP wasn't her *first* game, that title goes to "Princess Toadstool's Castle Run" an LCD watch game from 1990 that was only available at McDonalds. That barely counts, though.
I am genuinely hyped for the new Peach game. She hasn't had one of her own since Super Princess Peach, and while not a bad game it didn't look good for her first game to give her emotion-based powers. (Some people likened it to "the power of PMS".) The MacGuffin being the "vibe scepter" didn't help.