, whose name is Maria Laker, is the titular character in the novel Black Maria
(which has also been published under the title Aunt Maria
in some places).
Aunt Maria is a sinister old lady who lives -- and reigns -- in Cranbury-on-Sea?. Her house is not numbered, but her nephew Chris notices that no matter how you calculate the house numbers on her street, hers is number thirteen. She has a live-in companion named Lavinia, and a coterie of friends, chief among whom is her next-door-neighbor Elaine Blackwell.
Aunt Maria had a daughter named Naomi. She is aunt, by marriage, to Greg Laker, the father of Mig and Chris Laker.
She is also a Real Person.