Who is Evelyn Freemark from Running with the Demon and what is their importance?

Evelyn Freemark (Gran) is Nest's grandmother, and is married to Old Bob. Evelyn is familiar with the magic in the park, as the women in their family have all served as guardians of it. Grandpa, however, doesn't believe in magic. Evelyn was once the demon's lover, and eventually, the demon kills her.