I gave my now-husband, then-boyfriend a very thorough debriefing on my nmom before he met her. Just be honest and tell him what to expect and he'll be able to roll with it. Don't let her have the fun of deploying her N bag of tricks on him. Give him the playbook so he can know how to dodge and weave.

My debriefing went like this: My mom is insane. Not like, ahahaha what a zany character insane, but actually insane. She has many, many issues but here's what you need to know. She is always right, never apologizes, and is completely unaware or what constitutes appropriate behaviour in any situation. She will tell you things for the sole purpose of making you uncomfortable to watch you squirm. She will say inflammatory and provocative things to get a reaction from you, and then contradict herself moments later. Her opinions are fluid from moment to moment, but absolutely inert when you oppose them. She will comment on your physical appearance. She will make fun of you. She will ask detailed questions about our sex life. She will make fun of your family (whom she's never met) She will take any information you give her and extrapolate wildly to make you a bad person in her mind. You are never going to be able to have a normal, rational conversation with her. You will never be able to reason with her. She will panic for some made up reason about something she saw on the news and call you in the middle of the night looking for me to "make sure I'm ok". He's only spent two days with her and he experienced all the things I warned him about during that time.

But, he still married me and we happy as hell and live FAR away. Moral of the story: Be real with your man and prepare him for battle. Don't let him go in blind.