text: Early career O'Neill became involved in republican politics in her teens, assisting her father with constituency work in his role as a Dungannon councillor. She joined Sinn Féin after the Good Friday Agreement in 1998, at the age of 21, and started working as an advisor to Francie Molloy in the Northern Ireland Assembly. She kept this role until 2005, when she was elected to represent the Torrent electoral area on Dungannon and South Tyrone Borough Council, taking the seat which had been vacated by her father. O'Neill was elected as an MLA for Mid Ulster in the 2007 Assembly election, succeeding her Sinn Féin colleague Geraldine Dougan.
  While a backbencher in the Assembly, she sat on Stormont's education and health committees. In 2010, she became Mayor of Dungannon and South Tyrone. O'Neill was the first woman to hold the position of Mayor, as well as one of the youngest people. She held the council position until 2011.
  Ministerial roles
  O'Neill succeeded Michelle Gildernew as Minister for Agriculture and Rural Development in the Northern Ireland Executive after the 2011 Assembly election. One of her key decisions in the role was the relocation of the Department of Agriculture and Rural Development's headquarters from Belfast to a former British Army barracks in Ballykelly, County Londonderry in a bid to decentralise civil service jobs. The decision overruled an internal report on the matter, which recommended Strabane as a more appropriate location.