Sincere provided the voice for Mrs. Hogenson in the 2004 Pixar film, The Incredibles, directed by Brad Bird. She was cast in a recurring role as the Librarian in the FOX series, Glee, in 2010 and 2011. Her last role was in a guest appearance as Gloria on the Nickelodeon series, iCarly, in November 2012.
Sincere died from natural causes in Los Angeles, California, on April 3, 2013, at the age of 93. She had two children, Director Francesca Zambello and art dealer Larry Zambello. Her late husband, Charles Carmine Zambello, whom she married in 1949, died in 1992. She was a Christian Scientist.
