I like the idea of showing off different styles, and I also like the idea of her having more costumes than everyone else on the roster with 16. With that in mind, this is what I think it should be:
1. Basic style
2. An Asian-inspired outfit (I love me a good qipao)
3. A mature, high-end celebrity outfit (w/ bob cut)
4. An athletic, sporty look (w/ ponytail)
5. A dark-colored, gothic inspired outfit
6. Earthy, boho-chic (w/ long, wavy hair)
7. The preppy look (w/ glasses)
8. That edgy, rock and roll look (w/sunglasses and double Dutch braids)
9. Either a colorful, girly outfit, or pajamas
10. Lolita dress (with giant bow or headdress and long, straight hair)
11. Glitz/glamor (w/ hat); has to scream fabulous and over-the-top
12. Retro; inspired after an oldschool style, but still trendy
13. Vintage; straight up oldschool. Something very out of style, but still snazzy (complete w/ outdated hairdo)
14. Business attire
15. Sailor uniform; gotta have that one fun, blatantly playing dress-up outfit
16. A hip-hop inspired outfit (perhaps with a hoodie)
As for music, I think they should throw in a couple "that sounds like it's from a magical girl anime" type songs, to spice things up. Style Savvy's music is more varied than the (great) songs that are already represented in Smash. These would lowkey make really cool battle songs lol.