Shakky is Rayleigh’s business partner and wife.
[One Piece Manga Vol. 51 Chapter 498 and Episode 392, Shakuyaku calls Rayleigh “Uchi no hito” (うちの人; lit. person of my household), revealing that the two are a married couple].
Rayleigh had gone missing for the previous six months before her introduction; however, she was not worried because she knew what Rayleigh is capable of. Upon meeting Luffy, she informed him of the other major pirates (the Eleven Supernovas) that have arrived on the island around the same time as him. She then told them that they might find Rayleigh at Sabaody Park. After the Straw Hat Pirates returned from the Human Auctioning House, where they found Rayleigh, he and the entire Straw Hat crew gathered at Shakky’s bar. Rayleigh trusts her implicitly and he knows her qualities. With her deductions, Rayleigh managed to find Luffy after the war.