I'd say she has primarily told people to bugger off, but the sample size is her childhood friend who she obviously wants to remain friends with and Sei who initially she pushes away multiple times but her curiosity just keeps beating her logic.
Exactly. We already saw how Aya likes to put her faith in people. That’s why she went to Sei the first time. Then the third time, she was curious about Sei. I think the nakedness with Haruki was a combination of those things.
The whole getting naked was about truths. Haruki with her confession as well as her admittance that Aya’s bond with Sei is strong. With Aya, her attachment to Sei is further demonstrated with how she thinks about her while lying in bed with someone else.
I think it’ll give Aya much to think about, now that she kind of understands Sei and knows that she’s hurting Haruki.
"This girl used to follow Kurosaki-chan everywhere they say. Kinda super clingy, don't you think? This is a girls' school, so everyone's always hungry for a story." I'd hardly call that enough evidence to say that Sei tried to get with a student and not just a student that really liked their teacher.
I’m really curious to see what happened there. Maybe I’m expecting too much of the story but I doubt it’ll be something simple as Sei preying on a high school girl. Though I could of course be wrong.