According to the bride, Amber then proceeded to "bully" Katie about not being chosen.
"Amber (and keep in mind this is an eight-year-old child) told Katie that she'd never get married because she's too ugly. I could imagine how upsetting this would be for a child and I made Amber apologize and also took away the flower girl job and gave it to Katie," she explained.
The eight-year-old understandably didn't take the news well, and cried the entire wedding.
Her father then called the bride to tell her he was "extremely angry" at her for firing his daughter - but the bride defended her decision.
"As someone who was bullied myself growing up, it felt like [it was] the right thing to do after Amber's behavior towards Katie," she wrote.
"I can't imagine how upsetting those comments would be, and at that point, Katie, who had never been anything other than well behaved, deserved it more than Amber,"
Reddit users however were appalled that she hadn't just let both little girls be part of the wedding from the start.
"[You're wrong] for not just having two flower girls. Like, why was this even an issue in the first place?" wrote one user.
"These are eight-year-old CHILDREN, not adults dealing with other adults. Judging her very young relatives based on their looks is absolutely horrifying," exclaimed another.