@kent12121 Her daughter is mature enough to choose what to do with her love life, the problem is precisely that her mom still treats her like she is a little girl who needs her constant protection (I wouldn't even be surprised if she doesn't consider her an adult even when she turns 30).
Ishihara is old enough to be in a romantic relationship and trying to prevent that is extremely unhealthy so no, being her mother doesn't give her the right to do pull this sort of shit. It would be one thing if she was worried that MC might be a bad guy (ignoring the fact that a manipultive nutjob was going around claiming he was Ishihara's boyfriend without her mother even being aware of it) but she clearly doesn't think that, she is just a controlling bitch who thinks her daughter is unable to have any say on her own life.
Even taking all of this into account, I would probably be less annoyed by this if she explained her issues to MC in a clear and honest way but instead she chose to act like Vito fucking Corleone and approach the subject by throwing subtle threats and using cheap intimidation tactics, not to mention talking to him as if he was a brain damaged baby.
So yeah, she and her "right" can go fuck themselves. Bless MC for not accepting this sort of bullshit, I just hope he doesn't give in after she pulls her next bitch move.