My first guess would be that a professional baseball player might know how to handle this better than a 14 year old girl.
The problem I've seen is that the "have 'em throw their hands up" instruction at the plate conference often gets misinterpreted. Sometimes it's because the coaches just don't get it and sometimes it's because the umpire did a lousy job of explaining it.
Recent real examples I've seen:
- Temporary fence with open ends at the foul lines. Batted ball bounces through the opening. Fielder gives chase and is literally weaving in and out between lawn chairs and coolers to get the ball.
Umpires are calling dead ball but the runner keeps running. Runner gets a "home run" before the ball comes back to the infield. Umpires put runner back on second (ground rule double).
Offensive coach is livid. He's complaining that the umpire told the fielders to "raise their hands if it goes out of play" and also that "if the fielder goes after the ball it will stay live". Since this fielder didn't raise her hands, plus chased the ball twenty feet past the fence, coach wants it to be a live ball and "get whatever you get".
- Batted ball to base of fence. Fielder raises hands over head, just like the plate umpire told them to. Only it's not clear if the ball is really lodged or out of play. Umpires leave the ball live as the base umpire goes out to check on it.
Before he can confirm where the ball is, the fielder reaches down and grabs it. She had paused, but with the runner still running it looked like she panicked and thought she should make a play. Runner gets to third base.
Defensive coach goes bonkers. Wants it to be an automatic dead ball since his player "raised her hands" and wants the runner put back on second base. Umpires leave the runner at third, since ball was grabbed before it was confirmed as out of play.
"But you told us..." 
I don't tell them anything along these lines. When I go over the ground rules I note any boundry lines and say something like "if the ball goes in that area we'll award the appropriate bases." Let the coach tell his players what to do if it does. Leave it to the umpires to make the right ruling if it does. But no coach is going to be mad at me because I told him one thing, then seemingly ruled it another way, or because he just plain didn't understand what I told him.