See, jae in is right here bcos she wants sora to have a career before romance which is always the right choice. Period.
You see the reason sora is 1st bcos she got no friends and studies so people dont make fun of her. If she gets a bf and many more friends, you know what happens bcos she isn't a slightest bit mindful about her dropping scores. I know I sound like a boomer here. Plus Jae-in is creepy, no doubt there.
Lest assume Haena is a not a good character. Now what will u say about a girl who actually admires other girl and is worried about her safety and her company when she sees she is befriending a delinquent. Ofcourse Haena is a good character here bcos we know she is. In Jae-in POV, she is a bad influence on her competitor bcos she is from a delinquent school. But Your point is valid too. NO worries.
It is very rare to find a GL, where the main pair actually build trust rather than quickly kiss and sleep together. Good job.