Photojournalist Sabiha Mahmoud said the stranger was listening to her speaking and pointed at her, saying: “You lot are leaving next.”
The whereabouts of the incident has not been exposed.
Ms Mahmoud, a mother-of-two, wrote on Facebook: “Nationalism, fear and hatred has never served any country well.
“It is wholly inappropriate and insensitive to make jokes at this time when real people’s lives are and will be affected by this historically heartbreaking decision.
“Our opinions can be expressed without the name calling, alienating people and making sweeping generalisations which will only harden attitudes.
“Britain despite what you have put me through personally, I will not let fear win and I still hope you won’t either.”
Erdington MP Jack Dromey (Lab) said separately that the EU referendum and vote for Brexit has set free to “a tidal wave of racial abuse and attacks”.
Polish citizens of Birmingham have also been called “scum” and told to “go home”, he said.
The West Midlands Police and Crime Commissioner said he had received accounts of hate crime.
The Muslim Council of Britain cautioned the public of “countless incidents” of racism soon after the English Defence League held a rally outside a Birmingham mosque.