Monteiro's family last heard from her in May 1988, and she was last seen in July 1988 in New Bedford, Massachusetts. She has never been heard from again.

Monteiro was involved with drugs and prostitution at the time of her disappearance and foul play is suspected in her case. Her disappearance is believed be related to the homicides of nine other women and the disappearance of Marilyn Roberts in the New Bedford area. The murdered women's bodies were dumped along area highways in 1988 and 1989. Most of the victims were in their twenties and all of them had issues with prostitution and substance abuse. The murders, and Roberts and Monteiro's disappearances, remain unsolved.