O'Neill criticised for reunification pledge
Michelle O'Neill was accused of remaining wedded to the republican ideals of the past, after expressing hope that Ireland will be reunified during her tenure as Sinn Féin's Stormont leader.
She pledged to continue to work to convince people that they would be better off without a border.
Ms O'Neill (40) rejected the suggestion her party's desire to end partition meant it was not committed to making the power-sharing institutions work.
"We do believe in the Assembly," she said.
"The Good Friday Agreement was hard-fought for, it was the alternative to conflict, so we believe in the institutions that were set up under the Good Friday Agreement and we believe in making them work.
"Obviously we want a united Ireland and that's not a secret, but we do want the institutions to work and no one has worked harder than Martin McGuinness to make that happen over the last 10 years."
In recent discussions on what a united Ireland might look like, Sinn Féin has suggested the potential of retaining a devolved regional Assembly at Stormont - one linked to the Dublin government, rather than Westminster.
But DUP candidate Paul Frew said it was more of the "same republican priorities".
He questioned her priorities, saying: "Michelle O'Neill has been portrayed as a new face for Sinn Féin, but it is the same republican priorities that dominate her approach.
"Since being appointed by Gerry Adams we have heard nothing about Michelle O'Neill's vision for education, health or any of the real priorities for people's lives."