THE NORWEGIAN GEM will be christened by the Norwegian Cruise Line passenger who best personifies an "It" girl in an online video contest. NCL said that contestants can submit videos to the ship's Web site, gemitgirl.com, explaining what makes them an It girls like the Gem, NCL's final Jewel-class ship. The five finalists will be revealed on Nov. 15; and the grand prizewinner will be announced on Dec. 18 in New York, just before the ship is christened. The winner also will receive a seven-day cruise in the Gem's Garden Villa, along with her five-member "entourage," NCL said.