WHO SHOULD BE ASKED TO LEAVE??

I had an incident with a 7 year old dancer and another dancers mother.

We'll call one mom Sarah and her daughter Jane
the other we'll call Deb and daughter Mary
Both girls are 7 years old

Both girls, Mary and Jane are having a good time at a dance convention. Mary can be a little brat sometimes, but come one what 7 year old can't right?!

On the way home Sarah (jane's mom), has an outburst on 7 year old Mary. Telling mary how mad she was at her for treating her own daughter jane poorly. Sarah also told Mary that she does not want her to talk to Jane again, to basically stay away from her. Also telling Deb, that many other mothers have a problem with Mary. Deb had no idea how bad it was or if it was thrown out of proportion.

I think it was VERY inappropriate for Sarah, an adult, to lash out at a child who is 7 years old. I don't know why she didn't talk to Deb in private. and in reality what child, is not a little rude or snotty to others, and of course its no excuse, but children need to be constantly reminded. they are just children and they make mistakes.

So my question to you, my family and friends......

Who do we ask to leave. We cannot have the contention at the studio. So one or the other will need to be asked to leave.
Do we keep Sarah and Jane, and risk the possibility of losing more students, if Sarah has another outburst on another child that maybe said something mean to Jane, or do we keep Deb and Mary and continuously help Mary be a little more polite?

HELP!