I would agree that in 10U she should not have been out. Unless of course she purposely kicked the ball, or was looking at the ball as it hit her. I would have argued that if she had to wait until the ball passed her before running, then she was effectively being held back by the umpires the same as if it were a fly ball.
The runner doesn't have to wait for anything. The rule has been quoted.
The umpires have nothing to do with holding or sending a runner.....