Miss Maudie was Scout's favorite grown-up--aside from Atticus. Maudie always had time for the children, and she let them play in her yard whenever they wanted as long as they didn't bother her plants. She also gave them cake whenever she baked. Scout knew she could talk with Maudie just as she could with her father. Unlike Miss Stephanie, who couldn't be trusted, the children had "considerable faith" in Maudie. She didn't pry into their private lives, never told on them, and didn't play "cat-and-mouse" with them. She spoke with them just as if she was talking with other adults. Her speech "was crisp" and she showed "benevolence" toward the children. Scout particularly liked Miss Maudie's gold prongs that were attached to her eyeteeth. But above all, "She was our friend."
In Harper Lee's To Kill a Mockingbird, Miss Maudie becomes a closer friend to Scout when Dill and Jem begin to spend more time together: time that does not include her.
Scout describes that there is an agreement between Miss Maudie and the kids. They can eat all the scuppernongs ("grapes") they want (as long as they don't "jump on the arbor"), and they can have the run of her back yard. Miss Maudie works "ferociously" in her garden all day in men's overalls—something Scout can probably appreciate—though after dinner she is every bit the properly lady. Scout is young enough to appreciate seeing Miss Maudie's bridgework (partial dentures), something that firms up their "budding" friendship.
Miss Maudie is also a great baker and makes wonderful cakes, which she shares with the three kids. Miss Maudie knows some things about the Radleys, but I don't believe this is what draws Scout. It may be that Miss Maudie is a mother-figure, and that she also treats Scout with respect and appreciation, which Scout cannot depend on from her brother and Dill.