Failing to see something doesn't mean it doesn't exist. Are actions have huge impacts on others. I think even you can imagine the massive impact this would have on the lives of the parents.

Being a grandparents is a really big deal. You're right, it is still hurt decision. Her actions still affect others to some degree. Depending on what she does it has a huge impact on others. It makes total sense to be disappointed by the choices that other people make. It doesn't mean we don't like those people or that we hate those people but to deny that it has any impact or to mock someone for being sad about someone else's decision is choosing to not see what's obviously there.

None of us own our lives completely as our lives have huge impacts on other people. We owe tons to people around us. I think you would agree if we had a conversation about this even if we disagree on exactly what we owed to the people around us. Owing nothing to the people around us would mean that we can do anything we want anytime we want. It's too late for you to use the argument that as long as you're not hurting anyone you can do anything you want. I'm sure you probably can't see how that's the case cuz you can't see very much based on your comment. Several ways how that argument would be invalid including the fact that whether or not someone is being injured or damaged is extremely subjective and there are many ways that someone can influenced by our actions.

Wow I think I might be a psychic. Hmm, Yes I can see it now. I can see in your past when you found someone guilty of something unsavory because they didn't fight hard enough to stop it and we're implicitly consenting to it.

Yeah. It's not crazy to think that somebody wants something out of life. It's also not crazy to think that you want your kids to be happy doing something that has made you happy. Young people in every generation seem to imagine their life will be happiest if they indulge in every whim and pleasure that they desire. Not everyone grows out of that phase but almost everyone grows out of that phase. Eventually most people see that relationships bring us the happiest times of our lives. Some people say garbage like whatever makes you happy but in reality no cultures are that dramatically different from each other. It might feel that way sometimes but if you stand back just a little practically all cultures across practically all times have looked very very similar.

OP clearly stated that she wanted to cause damage to her relationship. It's right there in the first line.