Hollywood power producer Brian Grazer and Chau-Giang Thi Nguyen broke off their engagement last year, but she’s still sporting his giant rock. Beautiful pianist Nguyen — who we reported is dating Google mogul Eric Schmidt — was spotted last week at a dinner for interior designer Geoffrey Bradfield and BoConcept’s Shaokao Cheng, where she was wearing an “over-12-carat diamond ring” given to her by Grazer more than a year ago. When a guest asked why she was still wearing it, “she said he never asked for it back,” we’re told. Guests at the bash hosted by BoConcept included Sharon Bush, Liliana Cavendish and Douglas Hannant. Nguyen will play Carnegie Hall on Oct. 23.