She was working in a polling station in Mulcair's Outremont riding as an NDP scrutineer[11] when a friend texted her that she was leading Bloc Québécois incumbent Luc Desnoyers.

[12] In this capacity, she represented the NDP at the December 2011 conference on climate change in Durban, South Africa, where she denounced the Conservative government's environmental policies.

[14] Following the accession of Tom Mulcair as party leader, Liu was named deputy critic for science and technology.

On June 10, 2012, Liu attended the "Death of Evidence" march on Parliament Hill[15] which was led by groups of scientists following the elimination of the long-form census, the closure of the world-renowned Experimental Lakes Area as well as other cuts to environmental and scientific agencies contained in the Conservative Omnibus Bill C-38.

[17] On May 29, 2014, Liu tabled a bill aimed at protecting homeowners from excessive bank penalties for mortgage prepayment.

On June 16, 2014, Liu tabled The Intern Protection Act, which was seconded by fellow NDP MP Andrew Cash.

[21] After her defeat in the 2015 election, Liu completed a master's degree in Human Rights at the London School of Economics.