Rihanna is “really together”, insists her TV co-star Nicola Roberts.

Nicola, who is best known for being part of British band Girls Aloud, is one of the mentors on the reality TV show Styled To Rock and got to know Rihanna during filming.

Rihanna has recently been subject to reports that she is partying too hard and struggling with her love life.

She was also described as “emotional” by Oprah Winfrey after she interviewed the Bajan beauty.

“I don’t know about any of that [reports of Rihanna's struggles] but I just know that when I was working with her she was lovely and she was really collected, really together,” Nicola said of Rihanna on UK TV show This Morning.

Styled To Rock follows a group of wannabe fashion designers as they take on the challenges of creating stage outfits for pop stars including Katy Perry.

Rihanna is also an executive producer on the show and helps find the winner who will design a costume for one of her performances.

Nicola added that the global pop sensation was very involved in the project.

“She just knows what she is talking about and is really passionate about fashion. She really wants to give one of the contestants a real chance and a real shot and I think that is amazing,” she said.