Jennifer Lands was engaged to be Nick Valentine's wife. She is mentioned in a terminal in the BADTFL regional office and by Nick at the end of the quest Long Time Coming. Eddie Winter is suspected of having her murdered in August 2077.
The Bureau of Alcohol, Drugs, Tobacco, Firearms and Lasers received intelligence of associates of Eddie Winter inquiring about her, but chose not to place her in witness protection in order to not compromise the investigation.
Jennifer Lands is only mentioned in Fallout 4.