Nina Dobrev, Ian Somerhalder Too Close? Derek Hough Break Up Caused By 'Vampire Diaries' Stars' Lingering Relationship?

Are Nina Dobrev and her ex-boyfriend Ian Somerhalder too close after their break up? Was Nina Dobrev's break up from Derek Hough caused by her lingering relationship with her "Vampire Diaries" co-star and ex-boyfriend Ian Somerhalder?

According to IBTimes, Star magazine reported that Dobrev, 24, was spending a lot of time with Ian Somerhalder, even during her relationship with "Dancing with the Stars" pro dancer Derek Hough, Fashion & Style reports.

"Obviously her 'The Vampire Diaries' co-star still has a stranglehold on Nina," said the report, adding, "Once Derek really realized just how hooked on her ex she still is, he pulled the plug."

Allegedly, Nina even asked for Somerhalder's permission before she went on her first date with Hough, 28, who is the brother of her best friend, "Safe Haven" actress Julianne Hough.

However, a source told Us Weekly that the relationship between Dobrev and Hough "played itself out," and that distance also had a big role in their break up.

Hough is currently filming "DWTS" in Los Angeles while Dobrev is shooting "The Vampire Diaries" in Atlanta, Georgia.

"The distance was too much to handle," a source said of the pair.

As we previously reported, Nina and Ian have stayed close after their break up, presumably because they work together on "The Vampire Diaries." They frequently write to each other on Twitter too.

Ian Somerhalder posted a photo of himself on Twitter a few weeks ago, with an award he was given for his efforts in trying to promote environmentalism, Entertainmentwise reports.

Ian captioned the photo on Twitter, adding: "Thanks for snapping this shot- photo credit @ninadobrev from set of the Vampire Diaries Love Ian."

Nina Dobrev had her own message for her ex-boyfriend on her Twitter: "@Condenasttraveler Recognizes you for your relentless outreach+using it to change the world as you have+will continue to do. MAJOR Congrats!"

Ian responded with the tweet: "@ninadobrev @Condenasttraveler Awwww!Thank you NINA-thank you for the love&support.Truly. Xo Ian."