Auntie Matter (Debra McGrath) is Betty's great-aunt and Beatrixo's younger sister. The two have an extreme case of sibling rivalry and are always fighting. She has the ability to transform her body into a black hole and send all the things she sucks up into her body into deep space. According to her, this power comes from her father's side of the family, and Beatrixo is more like their mother, who has no powers. She was imprisoned on a distant planet called the Forbidden Zone until she was accidentally freed, however, Betty and Beatrixo managed to team up and imprison her once again.
Her name is a play on the word "Anti-Matter" (pronounced: AN-TIE with mostly the E sound and sometimes the I sound).