After a quick six month romance, Ian Somerhalder and Nikki Reed are engaged. While friends close to the couple are not shocked at how fast things moved between the two, Somerhalder's ex and "Vampire Diaries" costar Nina Dobrev is reportedly taking the news very hard.

"Nina is devastated over the engagement news," a source told Hollywood Life. "She can't believe this is all happening so fast."

Dobrev and Somerhalder dated for years after meeting on set of the CW show and split in 2013.

"She's completely shocked. She heard the news from mutual friends and can only shake her head in disbelief," the source added. "She knew Ian and Nikki were into each other but she never thought in a million years they would get married this quickly! It's a tough pill to swallow."

The source added that despite Dobrev's feelings about the engagement, she's going to remain professional while filming "The Vampire Diaries."

"Nina will put on a brave face and say all the right things. But inside it's killing her," the source told Hollywood Life.

Friends close to the 36-year-old actor said that the engagement was expected and Somerhalder had told Reed that he had "been in love with [her] for years," according to E! Online.

"They're so happy," the source continued. "They were crazy happy from the start. Their families love each other. It just feels really right."

Somerhalder and the "Twilight" actress have been serious from the moment they started dating. A few months into the relationship, they moved in together and in August adopted a pet horse named Eagle. Two months later the couple welcomed a kitten in to their family.

Earlier this week, Somerhalder also revealed that he had started a production company with the 26-year-old actress.

"Nikki and I are starting a production company and we're going to be able to tell even more stories that we really want to tell, everything from documentaries to TV shows to movies... all kinds of stuff," Somerhalder told E! earlier this week. "Having the success of a television show like [Vampire Diaries] really allows you to be able... now I get to start spreading my creative wings as well."

"It's going to be awesome," Somerhalder added. "Listen, it's about telling stories and it's about creating the content to tell those stories and whose going to distribute that content."