On January 11, 1962, she married the Polish author Jerzy Kosinski after a romance of 18 months. Kosinski 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 Kosinski to catalogue 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 Kosinski that Folger met her future boyfriend Wojciech Frykowski (Folger and Frykowski were murdered in 1969 by the Manson Family). In 1966, Weir divorced Kosinski, but she still remained a close friend. Weir was known for both her never ending volunteer work in many different areas, as well as her extensive travels around the world. She was also known to have battled many serious bouts of depression beginning as far back as 1950, and at times suffered from blackouts as a result of this. She also struggled with alcoholism for years.