She hounded the elderly man, shrieking: "You should go back to your country!"
He countered that Taiwan was his home, and though he was born in mainland China, he had lived and worked on the island for five decades. His words failed to stop the abuse: "You people are parasites. Get out of our country! You shameless Chinese!"
The woman, Ms Hung Su-chu, then chased the man, forcing him to wave his walking stick at her before a sympathetic passer-by stepped up and ushered him away.
A clip of the two-minute-long exchange which Ms Hung uploaded on a citizen journalism platform last Thursday has since gone viral in Taiwan, resurfacing the emotionally charged issue of the Taiwanese identity and the schism between "Taiwanese" and "Mainlanders".
The latter refers to migrants from China who arrived between 1945 and 1956 along with Kuomintang (KMT) troops who fled to the island after their defeat by the communists in a civil war on the mainland.
The video has also prompted calls by the opposition KMT for legislation banning "discrimination based on ethnicity".
In a rare move, Taiwan's political parties closed ranks, with President Tsai Ing-wen reposting a Facebook note by KMT chairman Hung Hsiu-chu decrying the video.
Ms Hung lamented that Taiwanese have been riven by "hatred". Since she became active on social media in the past one year, she has been dismayed by the use of derogatory terms such as "Chinese pigs" and "Chinese dogs" to describe the KMT and its supporters.
"Can our society stop fracturing?" she asked.
In reposting the note, Ms Tsai responded: "I am willing to start from myself. We need to condemn hate speech and stop ethnic prejudices from spreading."
Already, the episode has aggravated cross-strait relations, giving ammunition to Chinese media and netizens who cite it as an example of how Taiwan's pro-independence camp harasses its waishengren, which means people from outside the (Taiwan) province. Natives are referred to as benshengren, or people from inside the province.
Observers point out that Ms Hung, the shrill-voiced provocateur, is hardly representative of Taiwan. She is said to be a member of the Taiwan Civil Government, a fringe group that rejects the Taiwan government as illegitimate and wants Taiwan to be an American colony.
That said, the waishengren-ben- shengren fault line in Taiwan has its historical potency.
The former group has traditionally been seen as outsiders; the latter group - comprising three ethnic groups, the aborigines plus the Hoklo and Hakka who were descended from earlier migrants and who lived under Japanese colonial rule - are deemed "Taiwanese".
There is mutual distrust, given the different languages, attitudes towards the Japanese and the sense of identity, notes a 2010 essay on the subject by academics Dominic Yang Meng-hsuan and Chang Mau-kuei.
"The contested national identity - more specifically, the debate over reuniting with China or achieving de jure independence - has been identified as the most critical dividing issue between Mainlanders and native Taiwanese," they wrote.
Former president Ma Ying-jeou, for instance, was labelled by detractors as a waishengren who would sell out Taiwan's interests, given that his parents were from Hunan and he himself was born in Hong Kong.
But the lines today have become more blurred, says sociologist Peng Huai-chen from Tunghai University. Intermarriages and the passage of time mean that waishengren today comprise less than 10 per cent of Taiwan's population, he estimates.
"It's not a major issue any more."
Rather, he says, discrimination occurs more along the lines of economic status.
The man abused by Ms Hung was likely from the social underclass of poor KMT veterans, he adds.
Some others were also sanguine that the outrage prompted by the episode shows that the divide is closing. In a comment left on Ms Tsai's page, netizen Chan Ti-jan recounts how her grandparents were part of the wave of waishengren from Guizhou in China.
"From (the time when I was) young, people would tell me, you must learn to speak Taiwanese or you would be bullied by the Taiwanese. In this environment, I thought that Taiwanese people were really bad. But growing up and looking back, I feel that such ethnic prejudices can be shed."