This is part of the "updated rules" and I completely agree, again, with Final Word.
And also, at a U11 game, I'm not carding a player unless it was extremely reckless using excessive force.
My question is, if A&B are both charging for the ball, why is B already a foot out of bounds when she begins the slide?
Just to add:
•If the player is already off the field of play, play is restarted with a dropped ball
•If the player leaves the field of play to commit the offence, play is restarted with an indirect free kick from the position of the ball when play was stopped.