Loos was born in Madrid, Spain and only holds Dutch citizenship. Her father was Leonard Loos Bartholdi, a Dutch diplomat, and her mother (Elizabeth) is Anglo-Spanish - originally from Surrey. Growing up, she was privately educated. After moving back to Madrid in 2002, Loos worked for an American investment bank.

When former England football captain David Beckham moved to Real Madrid, Loos became his personal assistant during the transition period, alongside SFX agent and former Australian international Andy Bernal, who spoke Spanish fluently.

Beckham and Loos worked closely together both professionally and socially and Loos claimed that she became an "alternative wife". Victoria Beckham was not initially happy in Madrid, and wanted to develop her UK music career, so she spent much of her time in England. Loos claimed this resulted in Beckham becoming bored, leading them to spend almost all their time together socially, and a four month affair was the alleged result. Howe