Susana Werner said on Twitter that the robbery happened just before midnight on Wednesday in the city where hosts Brazil beat Mexico 2-0 in football's Confederations Cup.
"It was a routine robbery, just like all the ones I've heard about," said Werner. "It was the first time, but I was prepared to not react. The criminals were young and just wanted my belongings. There was no act of aggression, just a gun pointed at me."
Werner said she was driving when she suffered the robbery.
"I told them to take everything including the car but they let us go," she said. "Life goes on. I love Brazil and I have faith.
"It could have happened to anyone, there were three of them in the middle of the street, waiting for the first car which passed. I won the prize."
Crime is a major worry in Brazil, which will host the World Cup next year.
Car drivers are often held up at gunpoint when they are stuck in traffic and often prefer to run red lights at night rather than take the risk of being held up.
Violent crime also happens on buses, where gangs of armed criminals board the vehicle and demand valuables from the passengers.
Other forms of crime include so-called "express kidnappings" where the victim is put in a car, driven to cash points and forced at gun or knife point to withdraw as much money as possible.