Yes, I've had one bride dictate to me what my then 4 year old son should wear (he wasn't a pageboy, just a guest) and went to another extremely co-ordinated wedding - at least co-ordinated on the bride's side, so twee.
DD just suggested that her MIL and I chose colours which didn't clash with the general colour theme of the wedding, fair enough.
DIL was just very easy-going.
Choose a style which suits you, perhaps in a colour which doesn't clash. I doubt her mother will want to be wearing the same dress as you, what an odd idea.