Six is still so little. Others have given great advice but I wouldn't read too much into these things unless there's more to this picture. It sounds like, more than anything, this is annoying you. One thing you could try is that you close your eyes when she starts this. You could say, "The faces you're making are distracting me so I'm going to talk with my eyes closed for a bit." And just see what happens.
I don't allow chair gymnastics as a safety and budget issue.