Rosie was the name of a doll owned by Erin Hansen, which she later handed down to her daughter, Annika. Because Annika was an only child, and moved often due to her parents' work, she came to consider Rosie her best friend. (VOY short story: "A Ribbon for Rosie")
The last thing Annika saw with her Human eyes before she was assimilated by the Borg was the shattered body of Rosie. (VOY short story: "Maturation")