Well, Sylvia's going to make a forest of roses. Also, Sylvia is technically feeling better, but I still think the students would go easy on her, maybe give her the win and make her think she really won to boost her confidence. I'm also starting to notice Nobu's a lot like Kenji; is that how you usually play your characters?
Anyway, Sylvia will make her roses grow all around the building, encasing it pretty much and trapping the villains inside. Yasumi will stay outside right next to her and support her so that she will physically be able to do it, while Aina uses her martial arts skills to essentially blitz the villains from inside one of the flowers (that's how she will have gotten up there). If Sylvia's flowers aren't touching the weapon in order to properly secure it, Aina will go and get it herself, attempting to mess up the villains' relationship to dampen their teamwork in the process.