IT’S over between Ahn Duong and her husband, Bart Quillen. The half-Spanish, half-Vietnamese artist/actress and her blue-blooded groom were wed at the Devon Yacht Club in Amagansett two years ago. The engagement party had been held two months earlier in the River House duplex of Quillen’s grandmother, Betty Evans, whose family owned 1981 Kentucky Derby winner Pleasant Colony. Guests included Christopher and Amanda Brooks, Alison Sarofim and Jean Pigozzi. Duong, a painter who once dated Julian Schnabel and Simon de Pury, seemed to be a perfect match for Quillen, a collector of Czech furniture and antiques who co-owns the Prague Kolektiv showroom in Brooklyn. Quillen had no comment, but a source from the same social circles said, “She was high maintenance.”