Janina was a female Human colonist on Omicron Theta who perished on the planet when it was attacked by the Crystalline Entity in 2338.
Shortly before her death, Janina was the girlfriend of Raymond Marr. According to his letters, he enjoyed her gentleness, kindness, and her physical attributes. In 2368, Data told Raymond's mother Kila Marr about Janina, who hadn't known her son had had a girlfriend. (TNG: "Silicon Avatar")
This character was only mentioned in dialogue.