Dusty Jackson, 41, told Southgate police that the employee denied her request to add Timbits - small donut holes - to her order. She said it was "kind of f--- up" and "stupid" that the 16-year-old couldn’t fulfill the request.
Jackson called the employee an expletive, and the employee threw a cup of coffee at the woman, FOX 2 Detroit reported.
The coffee was warm – not hot – so Jackson suffered only minor burns as a result, and she declined medical treatment.
But she has decided to sue Tim Hortons over the Oct. 30 incident.
Abdallah Moughni, who represents Jackson, said that had the coffee been "black," his client would have been "permanently disfigured."
Police opened an investigation into the incident, but Moughni holds Tim Hortons responsible due to a similar incident that occurred in 2015.
"The blame is not so much on the girl who threw the coffee, the blame should be shifted to the guys in charge," he said. "The Tim Hortons Corporation, which allows this franchise and hundreds of franchises to poorly train, supervise and employ their employees."
Another employee, who witnessed the incident, said the victim "was just nasty from the start."
Michael Oliveira, senior manager of communications at Tim Hortons, told Click On Detroit that the company does not comment on pending litigation.
"However, I can say that Tim Hortons franchisees are expected to meet our brand’s strict standards and high expectations for guest experience and that we are looking into the matter with the franchisee that operates the restaurant," Oliveira added.