For Mia, you generally don't want to be too forward. For her second scene where you see her around campus, try just being nice and not overly flirty.
If you've already failed and continued, I'd recommend loading a save beforehand if possible, otherwise you won't be able to do her next scene (whenever I make it!)
Good luck <3
EDIT: if the scene still doesn't work, you can send me your save over on discord and I'll check if anything broke.