Your Mom sounds manipulative and no she should not have independent access to your kids to the extent that you control it.

15 yo is going to be out of your control soon, though.

OP. Get yourself into therapy instead of asking question a that literally no one could answer accurately without knowing the history. You sound a bit unhinged.

Yeah, no. If I were worried enough about someone’s interaction that I would consider blocking them, the relationship is over.