While it is never easy to listen to another player, parent or coach "bad mouth" one of your DD's coaches, I usually just let my DD's performance speak for itself......
Same here. With other players I will ask the parent if they go to lessons if they say yes, I usually ask if I can show them or change on little thing that maybe causing them to struggle whether it is hitting or pitching. If I hear the "my PC or HC says this", then I smile and wave and do my best.