Multiple realities(covers information from several alternate timelines)
Barbara Reen was a Starfleet officer in the 24th century. Her serial number was AR-058-1436 CDE.
In 2371, she was a crewmember aboard the USS Voyager. She was among the crew stranded in the Delta Quadrant, when Voyager was forcefully brought there by the Caretaker.
In an alternate timeline, her name was listed on the crew manifest read by Harry Kim in early 2372. (VOY: "Non Sequitur")
In 2376, her name was listed on a crew manifest. (VOY: "11:59")