Her empathetic response towards Muslims and against bigotry has received worldwide acclaim and she is now coming under pressure to take that stand in China.
Human Rights Watch described her leadership over the attacks as "extraordinary" in an open letter to her.
"Consequently we urge you to privately and publicly press President Xi Jinping and other senior officials to accept an international fact-finding mission to Xinjiang, the region of China in which the fundamental human rights of 13 Turkic Muslims are under sustained assault," said the letter signed by executive director Ken Roth and China director Sophie Richardson.
They said the Chinese Government promoted views that associated Islam with violence, terrorism and extremism.
"These contribute to anti-Muslim discrimination and to rampant virulent and derogatory attacks on Chinese social media against Muslim minorities, including recent ones applauding the Christchurch killings."
The group noted New Zealand's traditional preference for private dialogue on human rights issues and to confine such discussions to bilateral human rights dialogues - which are not held at ministerial or leadership level.
"New Zealand has just endured an appalling attack on Islam and its history as a tolerant nation. Your principled, unequivocal and evocative defence of Muslims and pluralistic societies is laudable," they said.
"We urge you to call on China's leaders to close the 'political education' camps, end Government-backed anti-Muslim statements, actions and policies and inform the leadership of New Zealand's support for urgent access to Xinjiang.
The Human Rights Watch letter comes after US Secretary of State Mike Pompeo renewed a call for China to end the detention of "hundreds of thousands" of Uighurs in Xinjiang and called it "abhorrent."
Speaking to reporters before the trip, Ardern said she was not sure whether the Christchurch massacre would change the dynamics of the visit.
"I don't know to be honest."
It had changed the nature of the visit because it was shortened to just Beijing and the business delegation had been dropped.
"Whether or not it will change the tone will in part, of course, come down to the way that my counterparts may choose to respond. I'm sure, in part, it will certainly be discussed up front but hard to know whether it will change the tone of the rest of the visit overall."
Ardern was clear that she was expecting China to raise the GCSB's knock-back of Huawei in Spark's 5G plans, and that she would be raising the ongoing negotiations to upgrade the 2008 free trade agreement between China and New Zealand.
She was less certain whether other sensitive issues would be raised such as the big power rivalry between China and the United States and China's militarisation of the South China Seas.
"But in positioning ourselves on those issues, it is never about picking sides. It is always based on upholding the international rule of law, maintaining a position of New Zealand's interests and very much taking a principled approach that isn't about the position of any other nation, regardless of whether they are partners or allies, but simply maintaining a position that responds to New Zealand's interests and independence.
"That is what I would highlight whether I was in a bilateral with the United States or a bilateral with China.
"New Zealand is not a nation that picks sides. We follow our interests and we follow our independence."
