Derek Hough, who just won an Emmy Award for Outstanding Choreography, has been dating Dobrev since August, sources told E! News.
Dobrev is close friends with Derek's sister, Julianne. The two vacationed together in Miami earlier this year.
"[Nina] was hanging a lot with Derek's sister Julianne," one source told US Weekly. "Then she fell for him."
Fans also noticed that Dobrev has been very attentive to Derek's season 17 turn on "Dancing With the Stars," often tweeting supportive messages to him and his celebrity partner, Amber Riley.
"Those of us touched by your light got to watch you brighten up the rest of the world. Keep shining!" Dobrev captioned an Instagram photo of Derek with his Emmy.
"@Derekhough !!!!!!!! #EMMYWINNER I cant express in 140 characters how unbelievably excited+incredibly proud I am of you. You deserve this :)," she also wrote.
Dobrev dated Somerhalder for three years before the two split last May, though they still send messages to each other on social media.