Julie was born on 1673 and, from early age, she was dressed as a boy, and was educated with them as well.
When the Twelfth Doctor said she couldn't sing well, she challenged him to a sword fight. He tried to avoid the duel by saying he carried no swords, but many were offered to him.
The sword fight was halted by Verlock, who warned Julie that those were forbidden, and she would be taken to the guillotine. She then replied that, if he wanted her head, he would need to take it himself. The two engaged on a sword fight, which Julie won, by stabbing Verlock. (COMIC: Terror of the Cabinet Noir)