Julianne Hough and Ian Somerhalder helped Nina Dobrev celebrate her birthday after the People's Choice Awards.

The 'Vampire Diaries' star turned 25 on Thursday (09.01.14) and her best pal and ex-boyfriend surprised her with a special cake shortly after midnight, just hours after they attended the glitzy awards ceremony in Los Angeles on Wednesday night (08.01.14).

'Safe Haven' star Julianne, 25, posted photographs from their cosy party on her Instagram site and a touching message about how much Nina means to her.

She wrote: ''Happy Birthday my beautiful @ninadobrev. You are kind, smart, adventurous, loving, honest, beautiful, mysterious, free, funny, and so on and so forth..... I am so lucky to call you my best friend! I love you so much... My sister!''

'Vampire Diaries' writer and executive producer, Kevin Williamson, also tweeted a picture of the surprised brunette actress holding the cake as Ian and Julianne hugged her from behind.

The group were also celebrating after Nina and her co-star Ian, who called off their three-year romance in May, picked up the prize for Best Chemistry at the awards, where they poked fun at their break-up.

The exes - who are constantly subject to rumours about getting back together - were visibly on very good terms during the ceremony and Ian even shared a special birthday message for Nina on Twitter, which she later retweeted.

He wrote: ''Happy Birthday @ninadobrev!!! The world loves you! We all do. Enjoy the moment, enjoy the day, enjoy the year!''

Disappointingly for fans of the show, Nina, who also briefly dated Julianne's brother Derek Hough last year, was spotted holding hands with a mystery man as she arrived on the red carpet before the ceremony.