“I love diamonds,” purred Nicole Kidman, bedecked in a diamond-covered Omega watch and impressive cushion-cut diamond stud earrings on Wednesday night at the Omega flagship on Fifth Avenue. Kidman — in town for four days to shoot the Omega ad campaign with Mario Sorrenti as well as to attend her husband Keith Urban’s concert at Madison Square Garden on Thursday night — was greeted by scores of both plainclothed and uniformed NYPD officers and an intimate crowd in the Omega boutique to sign Constellation watch boxes to benefit the United Nations Development Fund for Women. Fifty percent of the proceeds of the watch sales will go to UNIFEM. “We have a huge campaign to eradicate violence against women,” said Kidman, dressed in clinging black L’Wren Scott. “It’s a little boring,” deadpanned the starlet as she signed the final box. “Does anybody want to talk about anything?”