Cdonnee

This is a tough one, we have the opposite problem so I’ll come at it from the “grass is always greener” angle. We have never spent overnight time away without our child in 3 years because my in-laws are unwilling to do it. So for me, I’d probably be okay with childcare that differed from my own approach in exchange for the ability to spend a few days of precious adult time. Especially because it seems like the grandparent genuinely is willing to do it & enjoys spending time with their grandchild (which again, is something I’m sad my child does not get).
I don’t want to diminish that it’s frustrating & disappointing that she’s not listening & not respecting your direction, but what would be the alternative? Are you willing to hire someone for overnight child care? Are you ready to take your kid on every vacation you go on?
Since you are getting FREE childcare from family, maybe you can align with her somewhere in the middle on non negotiable vs negotiable boundaries (like be flexible on screen time, but hold firm on attending kindergarten). Then hopefully you can maintain that relationship with your in laws for your family. It’s hard when people parent differently, but Grandparents are only around for a finite amount of time so if it’s a special relationship, I’d figure out a way to be flexible.