Sinha was elected to Bihar Legislative Assembly in 2005 on the symbol of Lok Janshakti Party.

In the February 2005 Bihar Legislative Assembly elections, she contested on the symbol of Lok Janshakti Party.

She was victorious but political situation in state of Bihar in 2005 resulted in a re-election in the month of October the same year.

In the meantime Janata Dal United denied her their symbol for the Lok Sabha polls and Nagmani resigned from the JDU.

After Nagmani's Samras Samaj Party quit the third front and announced its support to Grand Alliance of Janata Dal (United) and Rashtriya Janata Dal, Sinha was fielded as the candidate of Samras Samaj Party from Morwa Assembly constituency of Samastipur district.