Who is Mrs. Merriam from Okay for Now and what is their importance?

Mrs. Merriam is the lady librarian at the public library. At first, she scolds Doug for sitting on the steps waiting for the library to open. As the novel unfolds, she starts to see Doug as a good boy. Finally, when Lucas comes into the library after returning from Vietnam, Mrs. Merriam asks if Lucas knows Lieutenant Merriam, indicating she has a loved one that is MIA in Vietnam.