No WAY. I have been on the receiving end of this and it is not nice. I was bridesmaid for my godmother and we had discussed me being her bridesmaid since I was very little so I’d been looking forwards to it for years. It was a very special and important occasion to me.
Somebody came with their daughter in a very fussy flower girl dress. I was an older child and the bride had chosen a bridesmaid dress which was quite understated. The net result was that all day people were making a fuss about the little flower girl and I was overlooked. Even at the reception there was an assumption from staff she was the bridesmaid and they tried to put her in my seat at the top table and had to be corrected. It was very disappointing for me.
The bride was fed up too because she took it as a hint and she deliberately didn’t invite this girl to be a bridesmaid because she knew she’d promised me the job years ago. Nobody could say anything either because who want to ruin a wedding with a row.
Please don’t do this OP. You always get people on these threads saying that they wouldn’t mind or they had a friend who didn’t mind, but they are not this bride. Some people do mind. You are running the risk of really upsetting someone on an important day. It’s an incredibly rude and selfish to do and just not worth it.
Incidentally the woman who did it at my Godmother’s wedding would probably tell you that everybody was fine with it. They were upset just nobody said it to the mother’s face. Please don’t do it, it’s a horrible thing to do.