Mitchell was born in New York City, New York. Mitchell, divorced, lives with her son in Boulder, Colorado. She has a daughter from a previous marriage who lives in California.
Mitchell attended elementary school in Putney, Vermont, and high school in Massachusetts and Idaho. She enlisted in the United States Army following high school, where she was trained as a truck driver, serving in Germany on REFORGER 1977. Following active duty, she served as a medic in the Army Reserves.
Mitchell first came to public awareness in 1988 when she founded an early fathers' rights group in Buffalo, New York, while she was studying pre-law at SUNY Buffalo. Upon moving to California to attend Stanford Law School she founded the first fathers' rights BBS which she ran from her student housing. That BBS later became the popular site DadsRights.org.
After graduating from Stanford, Mitchell opened a fathers' rights law practice, through which she represented fathers wishing to remain involved in the lives of their children following divorce. She spoke publicly and privately on the issues of fathers' rights and the need for children to have their fathers involved in their lives. Mitchell spoke, by invitation, to the California judges' bench Beyond the Bench program, to Santa Clara Family Court Services, and at Governor Pete Wilson's "Focus on Fathers summit.
In 1997, Mitchell produced and was the host of the cable show "Fathers are Parents Too". The half-hour television talk show "focused on the concerns, issues, and realities related to becoming and staying an involved father." Thirty-six episodes of "Fathers are Parents Too" were filmed in 1997, and were shown on cable television stations throughout the United States.
In 1998, Mitchell closed her fathers' rights practice, and changed her focus to Internet law and anti-spam efforts. She joined Mail Abuse Prevention System (MAPS), the first formal anti-spam organization, as Director of Legal and Public Affairs. While at MAPS Mitchell led the strategy for the first anti-spam lawsuits.
In 2002 Mitchell was asked to step in as CEO and co-founder of the newly created Habeas. A year later Mitchell left Habeas to found and run the Institute for Spam and Internet Public Policy (ISIPP), which was later renamed to the Institute for Social Internet Public Policy.
During her tenure at Habeas, Mitchell spearheaded the first ever Email Deliverability Summits, which became the impetus for founding ISIPP when she left Habeas.
Mitchell has been called upon to advise legislators on both family law and Internet law issues, most notably Attorney General Bill Lockyer of California, California State Senator Tom Campbell, and the offices of Arizona Senator John McCain and California Governor Pete Wilson. Mitchell authored a portion of the U.S. Federal CAN-SPAM law with Senator McCain's office.
Mitchell was also instrumental in creating the first forums in which Internet Service Providers (ISPs) and email marketers worked together. Other events which Mitchell led and which brought email senders and receivers together have included ISIPP's "Spam and the Law" conferences.
Mitchell has been involved in philanthropy since her early years. In 1978, when she was only 20, Mitchell spearheaded an effort to collect and fly mothers' milk to an adopted infant in Long Island, Cindy Callow, who required mothers' milk to survive and thrive.
In September 2005, Mitchell founded Auction Aid to help the victims of Hurricane Katrina, enlisting donated items from friends and colleagues Guy Kawasaki, Béla Fleck, Warren Farrell, Anne Fadiman, Eduardo Sánchez and Sir Harold Evans, to raise more than $5,000. Originally Auction Aid was created using eBay's "Giving Works" platform, about which Mitchell later wrote a scathing indictment.
In 2008, once again calling on her high-profile friends, who dug deep and donated to the cause, Mitchell worked with the United Nations World Food Programme and organized DushanbeRelief.org, an effort to raise funds for the country of Tajikistan, which raised more than $14,000 in a few short weeks to help the World Food Programme distribute resources to the people of Tajikistan during an historically harsh winter.
In 2013, Mitchell founded and organized PreventingSchoolShootings.com, a think tank dedicated to helping to identify youth at risk for becoming school shooters, to allow for intervention before they go down that path.