Wow!!!!
Congrats on your success. Even better in the face of all the verbal and emotional sabotage that is occuring!

I would tell them that you are simply maintaining your loss. Telling them you are going to lose more just adds fuel to the fire. They won't be able to distinguish another 5 lbs anyway.

Make it a complete non-issue by refusing to discuss it at all with any of them any more. Ask your bride to tell her mother to back off - it's none of her business anyway.

Good luck with your finishing touches!!!