Mavai has represented the Jaffna multi-member electoral district in the Sri Lankan Parliament since October 2000, firstly for the TULF, then the Tamil National Alliance.
She is the granddaughter of the man hailed as "Ezha Thanthai Selva" and "Sri lankan Gandhi" the Honorable S. J. V. Chelvanayakam, QC MP, Leader of The Federal Party/ TULF (1949–1977, a revered Sri Lankan politician and iconic leader of the Tamil community.