Marshall is actively involved in campaigning for the rights of displaced people. In November 2015, after completing shooting on Me Before You, Marshall travelled to Samos, Greece to volunteer with the refugees traveling from the Turkish coast to Europe. In June 2016 she spoke at the Next Century Foundation's Middle Eastern Migration Conference in Westminster on ways of countering human trafficking and modern slavery. In September 2016, Marshall was interviewed on the Arab News Network's The English Hour about her stance on the refugee crisis, immigration and combating prejudice and racism following the Brexit result. The program is modeled on the BBC's HARDtalk which is recorded in London, broadcast at peak time and subtitled in Arabic.