Great-Grandma Maxwell ( Gertrude ) is Nikki Maxwell and Brianna Maxwell's great-grandmother. She is very old and has only appeared in Book 1 (Tales of a Not-So Fabulous Life), and her second appearance has been made on a blog in the Dork Diaries official website. The blog can be viewed here.
When Nikki got a good grade in 1st grade in math by cheating, her parents sent a newspaper telling of this event to Great-Grandma Maxwell ( Gertrude ). However, she mistook her to be someone else.
Some years later, she asked Nikki to do a "funny Easter dance", but Nikki refused. Instead, Nikki's great-grandmother did a funny dance herself instead. Nikki calls it a "human pretzel". It's unknown if she's still alive.