BM dresses too sexy???

So i have been looking for dresses for my BM and trying to fugure out how to customize for my MOH and this is what i found and i think its perfect! Im not into the 'fru fru frilly willy' stuff that every one hates but never says anything because they are just good friends.
Any way i have been showing it to the girls who all say 'ooohs and ahhhs' but i when i showed it to my FSIL my FMIL was there (big mistake) and made the most horrified face. shes UBER religous, even though my FH and i arent, and she says they are in appropriate to sexy, not traditional. Shes already 'not happy' that we decided to get married at the RH instead of her chruch. What should i do? To be quite honest all my BM's are very curvacious (think beyonce on her day off) and even if i put them in trash bags she would probably think it was too sexy.