Kinda late, but you can also import Peach's model over Mario's and let her use Mario's animations. mibts did the latter in Super Mario 256, a hack that added two extra playable characters (Peach and Toade the Toad (sowwy guise, no Waluigi >:])), because adding custom animations (Peach's unused anims don't include attacking, carrying, death, Star get, swimming etc. animations) would be too much work (each character has over 100 animations). There's a tutorial in the General SM64DS Hacking subforum about replacing Mario's model with a custom one.