That would be a very petty grandparent. The grandchild has no say in the matter. This mom has already been through COVID with her son. It’s natural that she’s afraid for her baby, even though babies are in one of the least risky groups. Her son is probably also in a less risky age group, but he managed to contract it anyway. COVID isn’t a black and white situation. To vaccinate or not to vaccinate, it’s all a gamble. There are no guarantees either way.
That’s the breaks. Let the parents pay the kids education. They don’t want the family to visit, then why should the grandparents sacrifice for them. Maybe the Karen can get a second job to make up for what she cost the kids.