First runner up was Miss Botswana Emma Wareus followed by Miss Venezuela Adriana Vasini.
The 18-year-old Mills described herself as a positive, spontaneous, open minded and outgoing person on the official Miss World website.
The Miss World contestants spent a month in China, travelling to both Beijing and Shanghai before reaching Sanya on the southern Chinese island of Hainan.
It was the fifth time in eight years that the beauty contest was held on the popular holiday island. The final marked 60 years since the first Miss World competition was first held in 1951.