Flower Girl dress, who decides?

Is it customary for the bride to decide what her flower girl wears or can the childs mother veto the dress decision?
My sister is my matron of honour and says she will absolutely not let her daughter wear the colors I've chosen for my wedding.
I think the bride should be the one to decide this.....

Flowers and more

The private sale I did last month was VERY well received. I loved it. So, I'm doing it again. First come first served and don't be shy and think your selected items are gone. Sometimes it is just like an auction -- they come, they buy and then never pay, LOL. So an item that might be "sold" one day may be available again the next. A portion of these proceeds will go to a friend of mine on RCB who is having trouble paying for chemo medications. She has a piece of my heart and will soon have more of my money (which is always in somewhat short supply, LOL).

The Flower

A flower once flew high Beyond its earthly bonds Destined to the wind Where there it shortly flourished
Men wished that it could feel While journeying above Bloom petalled laughter To pervade the sky's Gray soup of winding paths And random gusts of chance Of gain or loss above them As below