The now-viral post received over 3,800 comments from Redditors who agreed that the OP's sister is wrong.

"Put your foot down that your sister will not be dressing like she is going to an MTV music awards show — or she will not be in your wedding," one person penned. "Because you are the damn bride, and in this case, you can control what your bridal party — and even guests — wear."

A second Reddit user agreed, writing, "Exactly. Being asked to adhere to a dress code for one day on one of the most important days in your sibling's life isn't a difficult ask, and following it is the considerate thing to do."

"NTA. That dress is totally inappropriate for your wedding," another Redditor replied. "This is also incredibly attention-seeking, and she's not the main character at your wedding. She should choose something else."

Someone else commented, "If it was at a wedding in my family, people wouldn't be offended. They'd just laugh at how desperate she seems." OK, that's a little harsh, but yes, we agree that the dress isn't appropriate for a wedding.

What do you think? Would you let someone wear a dress like that to your wedding? Let us know!