Teddy has been acting since the age of six, and made her acting debut at age 9 in 1995 in New Voices. During her early years, she worked hard on Guildhall and LAMDA examinations. By the age of 13 becoming the youngest to achieve a LAMDA Gold Medal for acting. She also studied Verse, Prose, Mime and Shakespeare. She had a regular role as Sima on the second series of the BBC1 sit-com All About Me (2002) and also played Amy Franks in the BBC's long-running radio drama The Archers. She has also guest-starred in Casualty (1986) and, more recently, appeared in Coronation Street (1960).
She then got signed to the UK record company Adventures in Music and released her first single "Don't Play Nice" under the name Verbalicious in February 2005. In January 2008, Will.i.am signed Cappuccini to Interscope Records via his will.i.am Music Group imprint. She was noticed for her demo EP Wommanequin, which she produced and wrote herself. Once signed to Interscope, she was placed with Cherrytree Records. Cherrytree encouraged her to find a name that was more direct and descriptive, and she then came up with the name Natalia Kills. (During this time she also wrote songs for French recording artist Matt Pokora and met underground director Guillaume Doubet, who as of 2011 now directs all her visual efforts in Paris.)
Sinclair released her debut album Perfectionist in April 2011 in Germany. She has also wrote, produced and co-directed a web mini-series titled Love, Kills xx (2010) and an additional film under the working title The Exhibition, which was made concurrently with the album, the soundtrack to the film. The album's first single, "Mirrors", was released in the United States in August 2010 and in the UK in April 2011. Her second single, "Wonderland", was released on in April 2011 in Germany. The song was featured in the 2011 film Beastly (2011).
Talking about if she ever think about coming back to TV] No, but my dream collaboration would be me and Tarantino, and I have a funny story about it... I was in the cinema a few weeks ago in West Hollywood, watching a really bad movie. It's a really tiny cinema that seats about 50 people, but there were only six of us in there at about two in the morning, and this man at the front of the theater he's laughing his head off, cackling, and the film is really sad, so it's totally inappropriate. He keeps laughing the whole film and it's totally driving me bonkers and then the lights go up at the end, he walks out with his date, and who is it? Tarantino. It was so funny. I've always had this dream of working with him and he's just right there.