Manalu has worked as a lawyer since she was 27 and works to aid victims of violence against women. In 1995 she joined LBHIskandar Muda Lhoksumawe as a lawyer. From 2000 she worked for LBH APIK Aceh, later joining their Board of Management. She has worked as commissioner of Komnas Perempuan since 2009 and was elected as Chair in 2015, a role she held until 2019.