Bill would often think of her mother, despite having never truly known her. She was often told that she looked like her, and she would imagine her mother telling her wise phrases despite her lack of presence.
Bill had no pictures of her mother, and upon telling this to the Twelfth Doctor after he had failed to deliver her a Christmas present, he travelled back in time to correct this. (TV: The Pilot)
When Bill and her friends moved into a new house, Bill brought a photo of her mother and hung it up on the wall. (TV: Knock Knock)