She can also respect that people have the right to say no about getting a booster, but then they have to respect that she can prevent them having contact with her child(ren) if they do say no, as respect has to go both ways.
Kimbles, it is her baby and she can do whatever she feels is right to protect her baby, no one is arguing that. People just need to keep in mind that even if fully vaccinated you are not 100% safe. If a vaxed person has been unwell at all even just a slight sniffle, they need to stay away from new babies, they may have the "less severe" case of w/c, but can still pass it on to the new bub and it may not be so "less severe" when the baby gets it. I offended many people with "just a little bit of a cold" when I wouldn't let them visit, vaxed or not. So if people are offended by being asked to have a booster, bad luck for them, but they do have the right to say no. If someone is offended for being refused a visit because they're sick that's also bad luck for them.