Most readers in comments treat past Meguro (and all 14yo girls in general) like a valuable vase they own which you shouldn't touch, it should stay on the shelf and gather dust, and if you touch it then you are a bad kid, you could drop and break it. They all forget to see her as a living being, which obviously had feelings, immature, childish, yes, but it was a huge experience in her life.
That's why I like seeing this fire burn from her thanking her "sensei".
Now throw some shit at me
You'd have a point if the guy she was with wasn't someone openly exploiting her feelings for sex and purposefully conditioning her to let men step all over her so he can have easy access to sex.
We know she wasn't like this in the past, too. This man is the one solely responsible for destroying her ability to have normal, functioning relationships.
This is not how one explores feelings/sexuality at a young age, this is simply being taken advantage of/grooming and it's repugnant.
Her view of those moments is completely tainted/biased because no one taught her what grooming/trauma is. She literally never got the chance to have a normal life because the teacher ruined it. Even if she herself doesn't see it that way, it's still horrible.
I'll give you this, victims of abuse irl do actually sometimes idolize their abuser and what they did as a coping mechanism (to basically separate themselves from victimhood), but that doesn't mean the abuse is any less bad.
However this manga just plays it straight and tells the reader the teacher did nothing wrong. It was just a different kind of love. That is appalling and is rightfully being lambasted in the comments.