I agree with a previous poster that said that you cannot let it go. How you respond now will be the benchmark for both the future treatment of your daughters and your future relationship. So think it through yes, but DO respond.
I would make it very clear that
1. You are the parent and when around you are not expecting them to do the parenting;
2. If they must discipline a child they CANNOT i the same breathe praise the other;
3. That if they cant deal with a spill, that you wont see them until such a time that you are confident that your daughters have “manners”.
So you ask them to choose between having a relationship with BOTH your children or manners.
I would not wait for my husband to solve the issue. Any other cause of frictions, i very much of the thought let your husband deal with his own parents. But in this case, it involves your children for which you are 50% of the parents. Therefore I would very firmly and politely set up the boundaries. I hate blatant unfair treatment.
A part of me would have wanted to spill my glass too in sisterhood with my daughter
. I wouldnt of course.
I would also explain to my daughter that she needs to learn to be careful and what can we do to help, but that Grandma shouldnt have overreacted. At the end of the day, it is a spill.
As for the ice cream i dont understand the issue. Grandma said no ice cream for ill mannered girl. If I was there and was the mother, I would have said.
“I m sorry but I call the shots. You have already overreacted to a glass spill and shout at my girl, I dont think I agree with the removal of the ice cream as well. You have made your point. Enough now”.