Bridesmaids doesn't want to wear her size vent

I do not know what going on in my friends head. She tells me in our bridesmaids group chat that her dress is too small and doesnt zip up. She refuses to get a bigger dress, she got a size 6 shell probably fit a size 8 might need a 10. My maid of honor got a size 8 even though she's a size 6 (she knows she can get the dress taken in easier then let out). My maid of honor offered to switch with my friend whos dress is too small and she flat out refuses. She's does want to get another dess and is adamant that the address to only doesn't fit because she was bloated. I tried explaining to her that it's easier to take a dress in than to let a dress out so if she just takes the 8 if she loses weight and becomes a 6 we can always get the dress taken in a size but she still refuses. I do not know what to say to her I just want her dress to fit and fit comfortably/ correctly. My maid of honor is ready to get her dress altered and once she does that my friend will no longer have a back up plan. She'll be stuck without a fitting dress. Like am I being crazy or like who really cares about your dress size as long as it fits comfortably??? Like it's a size 8 what's so bad about that just trade so you have a dress that fits please.