Just pray she gets to a size 22 then you won't have to put up with her at the wedding!
Just think, you only have to put up with the horrible lady for a day, her "friends" (if she has any) have to put up with her for a lot longer!
You have done fantasticly and I bet whiney woman has never even struggled with her weight and was saying the gym line to get the "oh but why you're not fat" line. You know like when teenagers say, "Oh I'm sooo fat!" Just so they can be bouyed up by their mates?!
Don't let it get you down, at least you are doing something about your weight rather than burying you head in the sand (like the other woman probably would do...!)