“It got serious really fast and they're inseparable," a source said of their fledgling romance back in September. “They're already saying ‘I love you.’”
Despite the immediate infatuation, the romance fizzled once the stars were forced to continue their relationship apart; Derek 28, is filming DWTS in Los Angeles, while Nina, 24, is shooting The Vampire Diaries in Atlanta, Georgia.
"The distance was too much to handle," a pal says of the pair.
Still, the split was a reportedly an amicable one, with Nina and Julianne remaining very much friends.
"Julianne understands -- there are no hard feelings," said a source.
Nina had previously dated co-star Ian Somerhalder, but the couple broke up in May after three years together.