Undercover Lover is the name used by a female love-meet.net user in Grand Theft Auto IV. No matter how many times Niko Bellic contacts her, she will never date him. She appears to be involved in the FIB witness protection program which has caused much of her profile, as well as her profile picture, to be censored. The rejection email sent to Niko is actually written by the FIB instead of Undercover Lover herself. Her name references the movie Undercover Brother, in which the main character refers to himself briefly as 'Undercover Lover'
There is a possibility that her photo may be a pixelated photo of Michelle as they share a similar hairstyle and that she reveals to be working undercover for the FIB which was revealed in the end of The Snow Storm.