Prior to serving in the Senate, she was a member of the New Hampshire House of Representatives, sitting as a Republican from the Hillsborough 16 district, having been first elected in 2014.

[2] As a State Representative Sullivan sponsored the Play Based Kindergarten bill which became law in 2018 and has been used as a template for Play-Based learning across the country.

[2] Sullivan also sponsored one of the strongest bills in the nation that criminalizes Female Genital Mutilation and has been recognized for her work protecting women and girls from this brutal practice.

[3] As a State Representative Sullivan also put in numerous bills to help combat the opioid crisis facing NH and in particular her city of Manchester.

Representative Sullivan served on the House Education Committee for four years and also served in House leadership as an Assistant Majority Leader Sullivan ran for Mayor of Manchester in 2019, losing to incumbent Joyce Craig in the city's non-partisan election, taking 43% of the vote to Craig's 57%.