My mother hated my wife with a passion. My mother has an extremely evil personality. She hasn't seen her grandkids since my oldests 4th birthday because she got lost driving over and "I'm sick of cell phones. No one needs a $&** cell phone" so we couldn't contact her to find out where she was and a 4 year old didn't wait 4 hours for her and opened her presents from everyone else that was there (now ex wife's entire WONDERFUL family.)
She is a huge reason for our divorce. Many other factors, but she is a big factor.
PSA for any mothers of boys here, when they get married, never tell your daughter-in-law "Oh, you can tell your pregnant, your face is getting fat." Also never say to your infant grandchild while changing the diaper, "Mommy's gonna have to shop at the big and fat store for you."
No matter how much support your son gives to his wife, this is going to affect their marriage.
Not to worry, not just the wife. She constantly told me how fat I was as well. And to this day she has no idea why my wife hated her even though we didn't talk to her for years and I talked to her since divorce and told her these exact things that she says.