Leong won her first American film role in The Mummy: Tomb of the Dragon Emperor, which was released in 2008.
Emperor Entertainment Group filed a lawsuit in the High Court on 3 April 2008, to seek damages from Leong for breaking a 10-year contract which Leong's mother signed for her when she was only 12 years old. Leong filed a writ against the company on 27 April. In November 2008, the legal battle between Leong and EEG ended in an out-of-court settlement, with the star "free to pursue her career".
In 2008, Leong met Hong Kong businessman Richard Li, son of billionaire Li Ka-shing, on a movie set, when she was 20 and he was 41. In April 2009, Leong gave birth to their first son Ethan Li Cheung Tsz. For this, Leong was allowed to use Li's family mansions in San Francisco. They also provided her with an entourage of caregivers, including five bodyguards, four full-time nannies and a personal attendant. Channel News Asia has speculated on whether Leong and Li have a prenuptial agreement. A 100-day-old banquet was held for her son from 9–11 July 2009, for three consecutive days, with some of the city's celebrities like Stanley Ho and his second wife Lam Wan Ying, and Tsang Yam Pui and his wife spotted in attendance.