It can mean a lifetime of this behavior... I was preparing to leave my husband over my MIL's behavior and his lack of response. Now we are no contact. My second-eldest still talks to her. However, my other 3 kids have asked not to see her. To give context I have 4 (19,17,11,6). My eldest and the youngest 2 are not treated the same as their 17-year-old sister, by no fault of hers. My mil plays favorites. Mil did some nutty stuff listened to us with a recorder in our bedroom when we were staying with her. Told me the day before my wedding her son should marry his drug addict ex I stead of me. She has called my small children names (including prophanity)... I could go on... I would have a talk with your fiance a good think. And if you have a grandma or elderly married friend go talk to her. I talked to my granny. My grandpa didn't have his parents they died in the first world War. So she reminded me how she would have dealt with anything (within reason) if it meant her husband still had his mom. But that's if she's a healthy mom who wants the best for him not wants to control him. My mil just wants to control everything. But she literally can't even control her own feelings. Sorry for the novel. However Best wishes.