[8][9][10] When Garrn was 13,[4] she was discovered during the 2006 FIFA World Cup in her hometown Hamburg, and then signed with New York agency Women Management.

[2] In the 2009-seasons, she walked over 60 shows for prestigious designers such as Stella McCartney, Dior, Louis Vuitton, Chanel, Hermès, Dolce & Gabbana, Michael Kors and others during fashion week.

Proceeds from the sales of her Closed T-shirt, her "Toni" jeans for women are donated to a charity that focuses on the education of young girls in Africa.

She appeared in advertisements for Calvin Klein, Prada, Versace, Cartier (fragrance), Jill Stuart, Fendi, Chloé, Emporio Armani, Hugo Boss, Zara, H&M, Dior, Donna Karan, JOOP!, Shiseido, Filippa K, J.Crew, Neiman Marcus, Givenchy (makeup), Tommy Hilfiger, Juicy Couture, Massimo Dutti, Max Mara, Peek & Cloppenburg, Express, Ralph Lauren, Burberry, L'Oréal, Biotherm, NARS Cosmetics, Mango, Ann Taylor, Blumarine, Aigner, Lancel, Alexandre Vauthier, Elie Saab, Calzedonia, Seafolly and Schwarzkopf.

[5][1] Garrn has worked with photographers like Steven Meisel, Peter Lindbergh, Karl Lagerfeld, Manfred Baumann, Paolo Roversi, Mariano Vivanco, Miles Aldridge, Craig McDean, Corinne Day, Camilla Åkrans, Ellen von Unwerth, Mert and Marcus, Victor Demarchelier, David Bellemere, Greg Kadel and Mario Testino.

Garrn was cast to play the role of Reeva Steenkamp in the 2017 Lifetime movie Oscar Pistorius: Blade Runner Killer.

The film chronicles Oscar Pistorius' conviction of culpable homicide after fatally shooting Steenkamp on 14 February 2013 in his Pretoria home.

In 2018, she appeared in Head Full of Honey by Til Schweiger and in Álvaro Soler's music video "La Cintura".

[20] She has hosted an annual fundraiser for her charity aptly titled "Supermodel Flea Market" in which donated clothes from celebrities and models are sold.