On January 11, 1962, she married the Polish author Jerzy Kosiński after a romance of 18 months. Kosiński had emigrated from Poland in December 1957 to the United States. Weir and Kosinski met in the summer of 1960 in New York City when the heiress hired the young Kosiński to catalog her private library. Weir was a close friend of coffee heiress Abigail Folger of the Folgers Coffee family, and it was through her husband Jerzy Kosiński that Folger met her future boyfriend Wojciech Frykowski (Folger and Frykowski were murdered in 1969 by the Manson Family). In 1966, Weir divorced Kosiński, but she still remained a close friend.