@allen133194 @Freestyle
I'm gonna call BS on both these.
Teasing a friend does not mean flirting nor does, well, being a friend and doing things friends do. Talking and joking with them? Hanging out? That's flirting? You really make it sound like you think a guy and a girl can't be friends because every action is a possible romantic pass- which is just plain wrong. Maybe the guy can misconstrue it as that, if they're being dense- but this is also why you talk to someone about these things and at the right time as opposed to when the person you're interested in is crying at the steps of school. She may or may not have known the guy liked her- but he never said anything to her either, until the worst moment possible. You can't dump all this on her.
Let's assume she thought he had feelings for her- so what? She wanted to be friends still, and not change that. So she tries to create a bit of distance between her and him, which might have been her way of sending him clues. Was her method the best approach? No, but that doesn't mean she's a terrible friend or some two-faced fiend. Heck, it may have even been a purposeful lie to avoid hurting his feelings, or maybe she was just avoiding the problem, who knows. Stepping back a bit, she even seems to try and give the male protagonist a chance in the first chapter to talk honestly about it, but he doesn't take the chance- she sets the stage and everything and he bails.
Let's assume she didn't know at all. So she didn't want her friend or others to know she was courting a teacher- which seems sensible, you don't always want your friends to know everything about you or your secrets, especially ones that are embarrassing or troublesome. Or maybe she didn't even care about that and just didn't want to have to explain it to others. Maybe she just wanted it to be something special between herself and the teacher with no one else butting in. If she sees the male protag as a friend, she doesn't have to tell him every little thing and spend all her time and every waking moment with him- do you expect that of your friends? In life people need a bit of distance to have healthy relationships, friendly or romantic, and to have time to sort themselves out.