While still a 17-year-old high school student, Shoshanna came to public attention by dating then 38-year-old Jerry Seinfeld, who was at the time starring in his eponymous sitcom. Early in their relationship, Spy Magazine referred to her as "a legal voter". They dated for approximately four years, from 1993 to 1997, before the relationship ended. She transferred from GW to UCLA in part to be with Seinfeld and cited missing New York City and constant press coverage as reasons for the relationship ending.
With a loan from her father, Zach Lonstein, chief executive officer of Infocrossing, she started her clothing company in 1998 with the mission to design a clothing line that appealed to different body types.
On May 10, 2003, Lonstein married Joshua Gruss, son of financier Martin D. Gruss and grandson of financier and philanthropist Joseph S. Gruss. Joshua Gruss is a Partner at Gruss & Co., a private investment firm based in New York City, and CEO of Round Hill Music. They have three children, a daughter, Sienna, born in 2005 who now Models for her, and twins, Angelica and Joseph Colby, born in 2012. The pair divorced in 2014.
Gruss has appeared in numerous television programs, webcasts, and interviews, including a 2008 episode of America's Next Top Model.
In 2013, Elizabeth Arden, Inc. named Gruss the brand's first-ever Style Director. In this new role, Gruss serves as a spokesperson and adviser for the design label.
Gruss is a Trustee of the Nightingale-Bamford School and also a member of their Alumnae Board Committee. Gruss is a founding chair of the Sesame Workshop family leadership committee and a founding member of The Rockefeller University’s Parents and Science Steering Committee. She is an active member of Congregation Emanu-El of New York. Gruss was Vice Chairman of the associate committee of the Memorial Sloan-Kettering Cancer Center and its Children’s Committee from 2012-2014.
