I'm in a very similar situation. One of my MOH's is very territorial and judgemental. Usually if we are at a gathering she attacks new people that she meets. Add to that the fact that she rubs my mom anfd FI the wrong way because she's judgemental.
My solution was to sit down and talk to her. I explained that at my dress fitting all I needed was creative criticism from her. I asked her to tone down her attitude and be nice to the sales people (she's the type that treats people ie waiters, salesreps etc as if they're beneath her because of the job they perform) And I told her it's my wedding day and my guest. I would love for her to be there but I'd love more not to be stressed.
Talk to her and explain your wishes, if she can't respect them she can gracefully RSVP not attending.