Allissa devotes a significant amount of time to pro bono work, focusing on immigration, children and civil rights. Her work has included teaching, advocating for policy change and direct representation. Allissa received the DLA Piper National Pro Bono Award in 2012 and in 2019.

Allissa has taken a lead role in DLA Piper's work to improve the treatment of the tens of thousands of unaccompanied minors who are apprehended each year as they try to cross the southwest border. In collaboration with Appleseed and Appleseed Mexico, Allissa helped draft the 2011 report, "Children at the Border: The Screening, Protection and Repatriation of Unaccompanied Mexican Minors." Since then, Allissa has worked on numerous projects for unaccompanied minors.

Allissa also represents clients in immigration proceedings. She has obtained Special Immigrant Juvenile Status for undocumented children who have been neglected, abused or abandoned and has obtained Legal Permanent Residence for domestic violence survivors.

Allissa has represented inmates in civil rights lawsuits against Texas prison officials.

Allissa has also developed curriculum and taught at a legal clinic at Houston's Covenant House, a shelter for homeless youth.