When You Reach Me
by Rebecca Stead
Louisa is Sal's mother and lives in the same apartment building as Miranda and her mother. She's a nurse who shares many of the same values as Miranda's mother. She helps Mom collect potato chips, for example, for the "pregnant-jailbird 'parenting group'" (26.5). She also gives Miranda time to talk with Sal during her visit to their apartment in Chapter 47.