In "Great Expectations," the reader doesn't meet Molly until chapter 26. Pip, and some of his friends are eating dinner at the home of Mr. Jaggers. He has a servant named Molly. During the dinner Jaggers insists that Molly show his guests her wrists. Molly begs Jaggers not to make her show her wrists but when he insists she relents and the guests observe that the wrists are very badly scarred.
"Jaggers' maid who serves dinner to Pip has strange scars on her wrists, as though she were once shackled. Indeed, she has known hard times before Jaggers has "tamed her," and Jaggers openly refers to her "gypsy blood."
Later in the book we learn that Molly turns out to be Estella's biological mother who has been raised by Miss Havisham.