Matilda would win this battle. :) Plus, I can see the Joker and Harley Quinn looking all shocked upon seeing Matilda using her telekinesis and stopping the weapons (which Joker and Harley would have) in their tracks, too. As a result, Joker would realize why Matilda dislikes those who are rude to her, and Harley would try to understand why Matilda does the things she does, only to see her as an enigma of sorts. :)