As far as I can tell, she wants her son and his fiancee and her family to dislike her ex and his new family as much as she does, without having to do anything to build a better relationship with them herself, and this is making her unhappy about the wedding. I think Carolyn's advice is good here - if she wants to be able to enjoy the wedding without mixed feelings, she needs to ditch the bitterness about the ex first of all. Or, alternatively, fix the mixed feelings by deciding that she values the bitterness more than her child's joy, and spend the wedding happily stewing in the bitterness.

(She also sounds like she's probably a miserable person generally, which may explain everyone's preference for the ex, but that's not the problem she's asking for help with.)