Avigail Levy is a Portal Keeper, and apprentice mistress to Rathna Stone. She is also deeply part of the Spitalfields Jewish community, with a large extended family. By the time Rathna comes into her life, her children and some of her grandchildren are grown adults, and she has a little space in her home to take in an apprentice. However, by the opening of The Fossil Door, age is catching up with her, and she is noticeably more feeble. Avigail Edgarton is named for her.
The Fossil Door
In The Fossil Door, Avigail talks about Rathna's assignment with her, and after Rathna and Gabe return from Scotland, she has some questions for him. It is clear by this point that she's come to regard Rathna as another of her family, and that Rathna returns the affection, even if neither of them directly talks about it.
(Click on the title above for more details about Avigail's role in that book.)