Cpl. Kelsey De Santis created a national stir last fall when she took to the Internet to ask celebrity Justin Timberlake to her Marine Corps birthday ball in a YouTube video. He said yes, and a friendship was born. Seven months later, Timberlake returned the favor, asking De Santis to attend the 2012 Spike TV Guy’s Choice Awards event with him last weekend in Los Angeles. In a phone interview, De Santis said it was surreal rubbing elbows with Adam Sandler, Channing Tatum, Aaron Rogers and other celebrities. She and her boyfriend sat with Timberlake at a table right near…