There's a number of events around the school that can do it. Just spend time talking to her, take her side on things, etc and it will rise over a few days.
okay, the thing is that i need to wait one more day till school starts again and i alr did my side quests so i cant really do anthing
Just go to Missy's bed and it'll start a new school day.
oh well, thank you i didnt know you could sleep.
Enjoy ^^
