Auntie Matter is Betty's great-aunt and Beatrixo's 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 asteroid until she was accidentally freed, however, Betty and Beatrixo managed to team up and imprison her once again. Betty's mother appears to not have inherited these powers, this may be because they skip a generation, It is not yet known if Betty has inherited these powers either.
She later returned in the season 3 episode "Wedding Crashers" and attempts to kidnap Jimmy and make him her husband, only to be stopped once again by Betty and Beatrixo. Since then, she has kept an eye out for not only Jimmy, but Admiral DeGill as well. Her name is a play on "anti matter".