She said he had allowed her "the most intense, the most painful and also the most exciting experience up until now."
The best actor prize went to Austria's Christoph Waltz for his flamboyant performance as a SS officer in Quentin Tarantino's World War Two caper "Inglourious Basterds," which also starred Brad Pitt.
Among the other awards, best director went to Filipino Brillante Mendoza for grisly crime drama "Kinatay" while Mei Feng, the writer for Chinese director Lou Ye's "Spring Fever," was honored for best screenplay.
The jury prize was jointly awarded to British director Andrea Arnold for urban drama "Fish Tank" and South Korea's Park Chan-Wook for vampire romance "Thirst."
The Camera d'Or award for debut film went to Australian director Warwick Thornton for "Samson and Delilah."
The ceremony brings the curtain down on 12 days of screenings, interviews, photocalls and parties in Cannes, where the global economic crisis curbed the normal extravagance and limited the number of A-list actors and celebrities in town.
However, Pitt and his partner Angelina Jolie did walk the red carpet for Tarantino's world premiere, and Mariah Carey, Penelope Cruz and Kylie Minogue were among the stars who made it to the palm-lined Croisette waterfront this year.