Who is Aunt Cilla from The Murderer's Daughters and what is their importance?

Aunt Cilla is Lulu and Merry's aunt. She is described as an unhappy woman, who blames everyone else for the bad things that happened in her life. When Joey kills Celeste, Cilla loudly voices her dislike for him. She doesn't even censor herself in front of Joey's children. She later blames Joey for her mother's death, claiming the stress of Celeste's murder added to her mother's stress. As a result, Cilla refuses to have Joey's children in her house and later sends them to an orphanage.