I'll have to look at the exact stats again, but I do remember that you have to have really high charisma and courage for her route (like somewhere between 8 and 12 I think?). Unfortunately there isn't really a way to trigger the encounter, though - it's totally random, and it's frustrating because you can't increase your stats after the event triggers. You kind of just have to keep playing and hoping it triggers at a time when your stats are good, and just like focus all of your free time and stuff on boosting your charisma and courage stats (and maybe your "bad student" stat to 3 at the start so you can skip class to increase charisma/courage). The event can trigger Tuesday morning or after I think.