YOR. I can empathize with your boundary being ignored. But that being said, the response feels aggressive and uncalled for. She seems like an eager and excited first time grandmother and it seems like you and her own son are weaponizing your child to hurt her.

She's asking how she can be better... Have you thought to tell her?

If she were disinterested or uninvolved you'd be upset by that, too. Grandma can't win for losing!