<human>: Earlier last week, my son stayed overnight with my mother while we were visiting (both sets of parents live 800 miles away). The next day, while at my in-laws, he blurted out to everyone "My other grandma said mom is too hard on me!". 

Obviously, my wife is hurt by this...not only because it was highly inappropriate, but she doesn't feel that she is hard on him (she's not)... but even worse is that my mom singled her out specifically. She didn't say "your parents are too hard on you", she said my wife is. My in-laws are upset over this too.

This has not been the first time my mom has been hostile towards my wife over ridiculous matters. After I got married, she expressed her disappointment at the 'Thank You' notes that she sent to family, saying her handwriting wasn't formal enough and that my wife did it on purpose as a sign of disrespect. A few years later she sent my then pregnant-with-twins wife a nasty email saying she was "disturbed" that my wife didn't post pictures of her visit to our home during Thanksgiving on Facebook. It was a high-risk pregnancy and she had several miscarriages prior; the last thing she needed was additional stress. 

After that incident, I told my mother that she would not have access to our family until she apologized. It took her over a year to finally say she was sorry, despite not having access to her grandchildren during that time and missing my twin girls' birth and baptism. Her apology was also very weak, but we all wanted to move past it.

I'm really not sure how to handle this one. I don't want to exclude her from my family again, but she needs to understand that this behavior will not be tolerated. She can't undermine my wife with my kids.

Give me the gist of the text in a nutshell
<bot>: My mother told my 8 year old son that she thinks my wife is too hard on him, and now I need to confront her about it but I am unsure how to proceed given our history.