Voice Lesson interruption

by Sara
(Minnesota)

My daughter has a weekly private voice lesson at school with her choir director. The girl that is scheduled to come in for the next voice lesson always arrives early. This would certainly be fine, except that she sits in the room and sings the songs along with my daughter, even sometimes walking to the piano and trying to plunk out the melody. My daughter has asked her to wait until her own lesson starts to sing as it irritates her. This is her time she feels to work on her piece for competition and she would never do this to somebody else. The problem is, the girl, even having been asked this more than once, continues to do this. Even more irritating, is the choir director actually said to her yesterday something to the effect that my daughter needs to go "more with the flow". Should my daughter just ignore this girl? I feel this other girl isn't being taught to respect others and that this just isn't proper by allowing her to do it week after week.