Why do a lot of Mother in laws behave like this? I hate to generalise but I will for this instance so as to gain some understanding. (I know there are fantastic ones).
So your son meets a lady and instantly the mum dislikes the lady. (Nothing wrong with the lady). I assume the mum fears loosing their son. What I don’t understand is by treating the lady poorly this is counter intuitive isn’t it? Because the lady is often the one to arrange the family. I know in my instance my MIL has never approved before it was even possible to know me. So inevitably her fears come true because why would I want to be around and promote time with someone for my family when they dislike me. It doesn’t make sense. If fear of loss was such a worry you’d welcome them so that they want to spend time with you wouldn’t you?