In his ramblings, Graham does not mention what she looks like, her name, or even why she was angry enough to harm him.
In 1934: Peter Pan in Chains, Graham goes on a particularly long rant regarding his sister. He tells Shaft that his sister one said to him that he "might as well have been rescued from a riverbank," and that he had asked in response if that meant he could marry her. She had then hit him with their father's wrench; he then realised that he had been rejected and that they must be truly related. He describes this as a happy yet sorrowful story of a gentle first love.
In 1935-A: Deep Marble, Graham brings his sister up while fighting Christopher Shouldered in a Martillo casino; he describes her as his 'long lost' sister and 'first love'. Christopher attempts to provoke Graham with his reply: if Graham stops gambling and finds a decent job, his sister might return. Graham ends up taking him seriously, and declares that he won't gamble ever again. Charging Christopher, he asks him how he should act if she does return someday, and by what name he should call her. He adds that if she is offended by his nicknames she might dislocate his neck with her own hands.
In 1935-C: The Grateful Bet, Graham informs the Gandor brothers that his sister once told him if he couldn't build something he shouldn't break it -- and then she hit him with a hammer. He concluded that construction and deconstruction are two sides of the same coin.
In 1935-D: Luckstreet Boys, Graham mentions that his sister taught him to value the lives of living beings other than humans.