Gastineau is the daughter of Lisa Gastineau and former New York Jets player Mark Gastineau.During the divorce proceedings between her parents she lived with her grandmother and attended public school at Clarkstown High School North in New City, New York. After graduating from high school she attended the University of Alabama before returning to New York City to model.
After moving back to Manhattan Gastineau signed with the Elite Model Management, and became an in-demand model as part of their celebrity division. Within weeks of signing with the agency, she appeared in a spread for Stuff magazine. She walked runways for Anne Bowen and Anna Sui during NYC fashion week in 2005, and signed an endorsement deal with L'Oréal Paris, which led to a European advertising campaign. She also became the face of high end casual wear designer Ed Hardy. She appeared on the cover of Steppin' Out, Hamptons and Lucire magazines. In 2005, she appeared on Maxim magazine's Hot 100 list, ranking at number 60.
