I personally would have held off on the out call until the coach said for certain, "she's coming out." At that point, once I call the out, she's out. The coach is responsible for his/her players and their well-being, and he/she alone should make the assessment if we're dealing with minors.
However, if at a later point in the game, she and the coach decide that she's well enough to play, let her back in.
Although, I have one question, since I don't have the rule book in front of me... Would this count as "re-entering" the game? She wasn't subbed out, but she is, by all literal accounts, "re-entering."