I don't really care for the story. It sounds way too generic because it's pretty much every Sonic game since SA1's story. If I were you, I'd find a way to take the last bit of it (with the emeralds being embedded in people) and expand upon it. Umm.. perhaps, unlike Sonic Team's done with Knuckles, give her a reason as to why she's destined.
Hit me up on AiM, actually.