What refrigerator object is Miss Stephanie like?
It can be argued that Miss Stephanie is like refrigerator mold.
In the story, Miss Stephanie is said to be an incurable gossip, a busybody, and the "neighborhood scold." It is Miss Stephanie who tells fantastic and unsubstantiated stories about the Radley family to Jem (who passes it on to Scout).
Scout relates that no one in the neighborhood trusts Miss Stephanie: as a gossiper, Miss Stephanie has the habit of making up damaging, mean-spirited stories about others and passing them on as truth.
In the story, Miss Stephanie makes unkind insinuations about Atticus's motivations for tolerating his children's presence at the trial:
Miss Stephanie’s nose quivered with curiosity. She wanted to know who all gave us permission to go to court—she didn’t see us but it was all over town this morning that we were in the Colored balcony. Did Atticus put us up there as a sort of—? Wasn’t it right close up there with all those—? Did Scout understand all the—? Didn’t it make us mad to see our daddy beat?
In short, Miss Stephanie is like refrigerator mold; just as mold renders jams, cured meats, and vegetables unsafe to eat, Miss Stephanie's stories damage the reputations of neighbors, friends, and foes alike.
You can read all about refrigerator and food mold from the link below.