As president of the student representative council in 2011, she led a productive campaign against the university's prevailing policy of race-based affirmative action in admissions.

After high school Ngwenya was awarded a scholarship to study medicine at the University of Cape Town, although she later transferred to a social science degree.

[4]During this period, Ngwenya led DASO's opposition to the University of Cape Town's prevailing policy of affirmative action in admissions, which used race as the sole proxy for disadvantage.

During her thesis research, she lived in New Delhi, India, working in competition economics for an American consulting firm called Nathan Associates.

[1][3] In 2016, Ngwenya became the first chief operating officer of the South African Institute of Race Relations (SAIRR), a liberal think tank then led by Frans Cronje.

[7] In December 2016 she was a vocal proponent of a pending vote of no confidence in the executive leadership of her alma mater; she argued that Max Price, the University of Cape Town's Vice-Chancellor, had made inordinate concessions to "unelected and unrepresentative" student activists in the #FeesMustFall movement.

[11] There were immediately rumours that she would be a candidate for higher office, such as the federal leadership of the DA;[12] Ngwenya said that she felt "that kind of pressure" but that "right now I am focused on policy".

[16] City Press reported that she was given a hostile reception by the progressive or social democratic camp in the party, which saw her function as being to put a "black face" to a conservative policy agenda.

"[12] Jason Lloyd of the Mail & Guardian argued in 2019 that Mmusi Maimane, the DA's federal leader and the champion of its social democratic faction, had made a "tactical error" in appointing Ngwenya, because she was ideologically opposed to the "race-conscious and transformative political outlook" for which she was tasked with developing a policy platform.

[17] In particular, Ngwenya was embroiled in a public spat over broad-based black economic empowerment (BBBEE), a government affirmative action policy which she opposed.

At a DA federal executive meeting in July 2018, she presented a policy paper entitled Vula: The open economy, which proposed abandoning BBBEE in favour of an environmental, social and governance index.

[31] However, after she won re-election in May, she announced on Twitter that she would decline her seat and would instead leave Parliament "to work now on issues at the nexus of tech and public policy".

[37] A fortnight later, News24 reported that Helen Zille, the DA's newly elected federal council chairperson, had decided unilaterally to reappoint Ngwenya to her former policy position, over the objections of some other senior party members.

[51] The success of the policy proposals, which some commentators criticised for "race denialism",[52] was regarded as a sign of the entrenchment of the liberal faction of the DA, spearheaded by Ngwenya and Zille.

[54] On 26 March 2023, shortly before the DA's next federal congress, Ngwenya announced her resignation from SAIRR to join Airbnb as the company's head of policy in the Middle East and Africa.

[58] In February 2020, Daily Maverick editor Ferial Haffajee suggested on Twitter that Gareth van Onselen's impartiality as a political journalist was compromised because Ngwenya was his "partner".