Your mother had seen it before you bought yours. you knew what you were getting, therefore should have gotten something different. It's ridiculous to expect your mil to change it at your whim when it was already bought and seen by your side. Definitely need to say sorry to your fiance and mil for your behavior.
Now lemme say things in a crystal clear manner:-
It's a kind of tradition, not obligatory, that the girl wears the dress bought by her in laws on the first day and the one purchased by her own parents on the second day...My Mil had suggested the other way round, like mine on the first and theirs in their reception.. But my mom didn't had to break the ritual and she said we wont mind following that custom !
But when we saw our sharara, it was so stunning that the one bought by my mil looked comparatively less likable and since our guest list goes up to almost 600 people on the first day, I thought that I'd be wearing mine because that's something people will be noticing most! I did so, whether selfishly or watever you call, because mil had assured us before that we can get it changed!
I've said what I had to, now it's upto you all if you guys can lend me some breathe of fresh air or continue accusing me of stupidity!