I agree with the power thing. Also I think mostly mothers are very much possessive about their sons and it’s difficult for them to share their possession like this, all of them know that no matter what they do Allah has created a very strong bond between husband and wife. No one can be closest than a life partner but they can’t accept this reality.
I believe that the MILs who show their actual reaction right on the face are better than those who try to be nice but they do play politics behind your back and can’t put themselves aside in those matters that are supposed to be between husband and his wife only. Don’t you think that such hypocrisy is much more bitter than anything else? 