Grandma, these kids are bullies. Don't do it if you are scared. And if they've decided you aren't grandma anymore because they can't push you around, I'd point out that they left you and since they are so independent you're going to get a new cat. Really. The parents are blackmailing you over a vaccine, what next? As the uselessness of the vaccine sinks in, they will probably miss you. They may well be angry now that you won't jump off the cliff with them.