Ask why. Maybe there's a reason. Or maybe she's just being lazy. Maybe tell her she's putting that effort into the wood of the piano instead of the keys. It's a lot easier to drop into the keys and let gravity do the work.
Have you asked her why she likes to play with hands in such a position?
Haha. Only a thousand repeats?I picture a little girl sitting at the piano resting her wrists on the wood board in front of the keyboard. Just using her fingers to play the keys. I'm wondering if that's right now. If I were the teacher I would probably keep reminding her and would probably do something like put my hand on my chin, tell her how much work it is to hold my head up... Stop moving my jaw when I talk because that is SOOOO much work... Maybe I could have someone push me around in a wheelchair so I don't have to walk. Start talking like that.Or does she hit her wrists while she plays? Maybe have her put her finger tips on the keys and move her wrist around.
She'll say, "I dunno." But I will ask her next week at her lesson = )
Then give her multiple choice for her to pick if she dunno. Sometimes when kids say "I dunno" they may be afraid of expressing themselves. Maybe she does not have the language to express why. Is it because she feels it easier to play like that? Is it because proper technique gives here some sort of problems. Does she feel pain in her hands? There must be a deeper reason on why she keeps insisting to playing her way. Most kids love to absorb knowledge.
How old is she? My teacher used to have a way to stop my younger brother doing that when he was younger: She compared his hands to water striders, the spiders that walk on the water. She said if the spider drops inward the water tension breaks and the spider sinks but if it stays up it stay above the surface. If she is young enough she might see what you mean.Of course she could be actively resisting you. "I dunno" could mean anything from "I actually don't know" to "I 'm too lazy" to "Because I hate playing piano".
If she's seven, tell you just painted or stained and varnished the piano. She can't put her hands on the wood part. It's not allowed. So cruel... (Bob wonders if there's a way to put tacs on the wooden part of the piano.)Make it game. Or bribe her and give her a sticker if she doesn't.
Instead of tacs, you might run an electrified wire along the board piece below the keys. It's less obvious that way. You know how children like surprises. Just tell her it's static electricity. She's seven. She won't know the difference.
I see it as follows: For what reason are you trying to change her behavior? Apparently it hasn't caused a problem for her yet, or she would already have tried to fix it herself. If there comes a time when this behavior becomes limiting (She cannot play what she wants how she wants it) or deleterious (She is suffering from a mysterious pain in her hands), then you can suggest this solution to her and no doubt she will jump at the chance to try it. Now, WE know that in the future this can cause problems, but I think she might have something else on her mind; such as trying to read the music, figure out the right keys and press them, or whatever. It might be useful to try and figure out what she IS paying attention to instead of her wrists. Then maybe you might work on that until she feels she has overcome it? Dunno.