Mom talking poorly about fiance to family members

How do I deal with my uBPD mom talking poorly about my fiance to my aunt and cousins? According to my brother he overheard her saying some pretty nasty things. He treats me like a queen and provides and does everything for me but she still finds something to complain about. And she absolutely will lose her shit if she even thinks we are talking about her to anyone. The hypocrisy is maddening. We were going to visit for Christmas but how can I bring him around her knowing this is how she truly feels? Do I confront her? She will likely deny if I do so but I’m just sick of allowing her get away with being a shitty hypocritical person.