Simmons graduated from Vassar College and was a Rhodes Scholar at Lincoln College, Oxford where she began studying female aggression. She is a native of Rockville, Maryland, her mother Claire is a Jewish historian and her father Luiz R. S. Simmons is an attorney and a member of the Maryland General Assembly.

Odd Girl Out was made into a TV film starring Alexa Vega and reached No. 4 on the New York Times Best Seller list.On September 1, 2009 Simmons was interviewed on NBC's The Today Show about her new book "TheCurse of the Good Girl".