Singer Rihanna poses at the amfAR's Fifth Annual Inspiration Gala in Los Angeles, California October 29, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna poses at amfAR's fifth annual Inspiration Gala in Los Angeles, California October 29, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna poses at amfAR's Fifth Annual Inspiration Gala in Los Angeles, California October 29, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna poses at amfAR's fifth annual Inspiration Gala in Los Angeles, California October 29, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT TPX IMAGES OF THE DAY) 

Singer Rihanna poses at the amfAR's Fifth Annual Inspiration Gala in Los Angeles, California October 29, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna poses at the amfAR's Fifth Annual Inspiration Gala in Los Angeles, California October 29, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna arrives for the Council of Fashion Designers of America Awards (CFDA) at Lincoln Center in New York June 2, 2014. REUTERS/Carlo Allegri 

Singer Rihanna arrives for the Council of Fashion Designers of America Awards (CFDA) at Lincoln Center in New York June 2, 2014. REUTERS/Carlo Allegri (UNITED STATES - Tags: ENTERTAINMENT FASHION TPX IMAGES OF THE DAY) 

Singer Rihanna arrives at the 2014 MTV Movie Awards in Los Angeles, California April 13, 2014. REUTERS/Lucy Nicholson (UNITED STATES - Tags: Entertainment) (MTV-ARRIVALS) 

Singer Rihanna arrives at the 55th annual Grammy Awards in Los Angeles, California February 10, 2013. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) (GRAMMYS-ARRIVALS) 

Singer Rihanna performs during the Victoria's Secret Fashion Show in New York November 7, 2012. REUTERS/Carlo Allegri (UNITED STATES - Tags: ENTERTAINMENT FASHION) 

Singer Rihanna performs during the 11th season finale of "American Idol" in Los Angeles, California, May 23, 2012. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT TPX IMAGES OF THE DAY) 

Singer Rihanna arrives at the Metropolitan Museum of Art Costume Institute Benefit celebrating the opening of the "Schiaparelli and Prada: Impossible Conversations" exhibition in New York, May 7, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENTERTAINMENT FASHION) 

Singer Rihanna performs on NBC's "Today" show in New York, May 27, 2011. REUTERS/Brendan McDermid (UNITED STATES - Tags: ENTERTAINMENT) 

Rihanna performs at the Nilson Nelson Arena in Brasilia
as part of the "Loud" tour September 21, 2011. REUTERS/Ueslei Marcelino (BRAZIL - Tags: ENTERTAINMENT TPX IMAGES OF THE DAY) 

Rihanna arrives for the BRIT Music Awards at the O2 Arena in London February 21, 2012. REUTERS/Luke MacGregor (BRITAIN - Tags: ENTERTAINMENT) (BRIT-ARRIVALS) 

Rihanna carries the International female solo artist trophy during the BRIT music awards at the O2 Arena in London February 15, 2011. REUTERS/Luke Macgregor (BRITAIN - Tags: ENTERTAINMENT SOCIETY)

Singer Rihanna poses in an outfit designed by Jean Paul Gaultier upon arrival at the 53rd annual Grammy Awards in Los Angeles, California February 13, 2011. REUTERS/Danny Moloshok (UNITED STATES - Tags: ENTERTAINMENT) (GRAMMYS-ARRIVALS) 

Singer Rihanna poses on the red carpet at the Metropolitan Museum of Art Costume Institute Benefit celebrating the opening of Alexander McQueen: Savage Beauty, in New York, May 2, 2011. REUTERS/Eric Thayer (UNITED STATES - Tags: ENTERTAINMENT FASHION) 

Rihanna arrives at the 54th annual Grammy Awards in Los Angeles, California February 12, 2012. REUTERS/Danny Moloshok (UNITED STATES - Tags: ENTERTAINMENT) (GRAMMYS-ARRIVALS) 

Singer Rihanna performs at the 2010 American Music Awards in Los Angeles November 21, 2010. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT)(AMA-SHOW) 

Singer Rihanna performs at Madison Square Garden in New York August 12, 2010. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna performs at the Nickelodeon Kids' Choice Awards in Los Angeles March 27, 2010. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) 

Singer Rihanna adjusts her hair while performing at an outdoor concert in New York's Times Square during an appearance on ABC's Good Morning America, November 24, 2009. REUTERS/Finbarr O'Reilly (UNITED STATES ENTERTAINMENT) 

Singer Rihanna poses with her awards for favorite female artist in the pop/rock and soul/R&B categories at the 2008 American Music Awards in Los Angeles November 23, 2008. REUTERS/Phil McCarten (UNITED STATES) 

Musician Rihanna arrives for the 2009 Glamour Women of the Year award show in New York November 9, 2009. REUTERS/Lucas Jackson (UNITED STATES ENTERTAINMENT) 

Rihanna performs "Wait Your Turn" at the 2009 American Music Awards in Los Angeles, California November 22, 2009. REUTERS/Mario Anzuoni (UNITED STATES ENTERTAINMENT IMAGES OF THE DAY) 

Singer Rihanna performs "Umbrella" at the 2007 MTV Video Music Awards in Las Vegas September 9, 2007. Rihanna won the award for Monster Single of the Year for the song. REUTERS/Mike Blake (UNITED STATES) 

Singer Rihanna arrives at the 2007 American Music Awards in Los Angeles, California November 18, 2007. REUTERS/Mario Anzuoni (UNITED STATES) 

Singer Rihanna performs on NBC's 'Today' show in New York June 8, 2007. REUTERS/Brendan McDermid (UNITED STATES) 

Singer Rihanna arrives for the annual Fashion Rocks concert in New York September 7, 2006. REUTERS/Eduardo Munoz (UNITED STATES) 

Rihanna performs during the Jingle Ball concert at Madison Square Garden in New York December 15, 2006. REUTERS/Eric Thayer (UNITED STATES)