An Ontario woman and her family are suing Canada’s best-known coffee chain for C$500,000 ($366,000), alleging Tim Hortons served her “superheated” tea in a defective cup that left her with “horrific” burns on her body.

Jackie Lansing, 73, ordered a black tea while at a drive-through in southern Ontario last year.

Lansing, who was in the passenger seat of a vehicle, picked up the cup, which “immediately collapsed in on itself”, according to her statement of claim.

“As a result, approximately 14 ounces of scalding hot liquid spilled on Ms Lansing’s stomach and legs,” her claim reads. “The tea provided was a hazard rather than a beverage.”

Her lawyer Gavin Tighe told the Guardian he believes the company was negligent both for the temperature of the tea and the construction of the cup.

“What began as a routine occurrence, buying a cup of tea, in the blink of an eye turned into a life-changing injury that required multiple hospital visits and has left both physical and emotional scars,” he said.

According to the statement of claim, Lansing’s injuries required morphine to treat the pain and that it took three weeks for the wounds to close. She is now “permanently and seriously injured … and disfigured”.

Lansing alleges that she now suffers hypersensitive skin that requires constant treatment, experienced weight gain and is now “frequently afraid … gloomy, depressed and tearful”.

Lansing’s daughter is also seeking damages under the province’s Family Law Act. She alleges her mother’s injury has meant she has not been able to fully care for her disabled child.

TDL Group Corp, the licensing company of Tim Hortons, and Greenwood Enterprises Inc, the operator of the franchise, all denied allegations of negligence.

In their statement of defence, they argue Lansing “assumed risk” when ordering a hot beverage and that “she was the author of her own misfortune” when the tea spilled. The defence, which also suggested Lansing was distracted by her mobile phone, is requesting the court dismiss Lansing’s claim.

The case is reminiscent of Stella Liebeck’s fight against the fast-food giant McDonald’s in 1994. The 79-year-old New Mexico widow suffered life-threatening third-degree burns and was awarded $2.7m by a jury in punitive damages – but her case was widely mocked on late-night television.

Tighe acknowledged that Lansing’s case was also likely to be ridiculed.

“This isn’t a ‘boohoo, woe is me’ situation. Nobody would say they’re prepared to get burns like this. Buying a cup of tea where the cup then collapses? Nobody’s buying a ticket for that lottery.”

Instead, he hopes the lawsuit prompts a change to how the coffee giant serves its beverages.

“Lots of people order tea and coffee from drive-throughs. If this stops one of them from getting burned, then it’s a useful exercise,” said Tighe. “Nobody wants cold tea, but nobody wants their tea brewed in a volcano either.”