Interesting thread and discussion. And a good example of the kinds of decisions that umpires are forced to make "on the spot" in any number of games, where there is no clear cut rule to address the issue and no matter what you decide- no matter how well-intentioned- somebody isn't going to like it.
First off, I will disagree with anyone saying that the umpires "overstepped their authority". Actually, they acted within their authority. Rule 10 (
you know, the rule that nobody ever bothers to read, because it covers the umpire's duties ) empowers the umpires to make decisions on any point not specifically covered in the rule book. Issues with player safety would fall under that jurisdiction.
Having said that...my personal opinion leans toward letting her pitch. Having the right to do something (prevent her from pitching) doesn't always mean it is the right thing to do. Generally, umpires are not responsible for evaluating the skills of the players or their ability to protect themselves from every possible injury. That responsibility lies with their coaches and parents.
You can "what if" these scenarios to death and second guess any decision. What if...the player got moved to the outfield...then got nailed by a fly ball because her glovework was weak? What if...she was batting and, due to an inability to grip the bat properly, she lost it on a swing and it hit another player? What if...she was allowed to pitch, but because of the "glove switching" was not able to meet all of the pitching requirements that any other player is held to (bringing the hands together to start the pitch, no "double touches", etc).
But all of that is impossible to predict. Just as a certain injury at the pitching position would be impossible to predict. If her parents are comfortable with her pitching, and her coach is comfortable with it, as the umpire I lean toward letting her pitch.