Hattie was part of a band from the 40th century.
After one of her concerts of the Twist, the Twelfth Doctor took her bass, so she began following him. Later, Hattie and the Doctor met Jakob, who had been accused of killing Idra Panatar, but claimed to be innocent. The three started investigating what happened, and met the Foxkin, a race who kept their existence unknown to the rest of the Twist. As the Doctor, Hattie and Jakob had found them, the Foxkin said they would have to be either killer or imprisioned. They were sent to jail, but managed to escape.
Then, the Doctor revealed that he had discovered, by acessing the data of Jakob's byonic eye, that he indeed killed Idra. After this, the Doctor invited Hattie to travel with him. (COMIC: The Twist)
While travelling together, the Doctor and Hattie were playing their guitars together, when Hattie warned the Doctor that the TARDIS was making a noise. When the Doctor discovered the cause of the noise, he said it was an emergencial landing. When the Doctor and Hattie left the TARDIS, they found an abandoned house. Despite Hattie's desire to return to the TARDIS, the Doctor insisted upon going inside it and finding out what caused the TARDIS to land. (COMIC: Playing House)