Spoiler warning: Plot and/or ending details follow.
Musiker was Admiral Jean-Luc Picard's first officer aboard the Federation starship USS Verity in the year 2385, during their ongoing mission to relocate Romulans from planets that were threatened by the Hobus supernova. Musiker, with the rank of lieutenant commander, was Starfleet's leading analyst specializing in the affairs of the Romulan Star Empire. During the course of the long mission, she had taken to calling Picard by his initials, "J.L.", dismissing the formality of calling him by his rank.
The Verity traveled to the Romulan colony at Yuyat Beta, in preparation for relocating the 10,000 colonists. Musiker and Picard were asked by Major-Domus Athus to beam to the planet to visit the colony leaders alone. Picard and Musiker were shocked to learn there was a native population of humanoids, 4 to 5 million strong. When Picard protested evacuating just the Romulans, Governor Shiana had Picard and Musiker imprisoned, cutting them off from the Verity in orbit. (PIC - Countdown comic: "Issue 1")
After Admiral Picard's resignation in 2385, Raffi began a long decline, eventually losing her security clearance and position in Starfleet. By 2399, she was estranged from her husband and son, and living in a small home at Vasquez Rocks. She had become acquainted with Cristóbal Rios well before then, having said they had known each other for years. (PIC episodes: "Maps and Legends", "Stardust City Rag", "The Impossible Box")