What would you do?

[Adam]

Originally Posted by Rufus

As she dribbles up the court her hand moves under the ball (clearly under, not just on the side) and the ball comes to a rest.

I blow the whistle and give the signal for a carry. We were briefed, and expected, to let the kids know why we were calling violations/fouls (this was a pre-season kick-off tournament) so I let her know what she had done. She gives me a look like "Whatever" and we go the other way.

Next trip up the court you guessed it, ball comes to a rest in her up-turned hand. I blow the violation again. Coach says "Tell her what she did wrong." I say "Coach, I did".

Hmmm. Keep calling it, don't tell her why after her little comment. If it's as obvious as you said, I'd probably call it regardless of defensive pressure.