Ms Zhang says the crash happened in a line of stationary traffic, after her foot slipped off the brake of her automatic transmission car. She had been driving away from a licensing centre, upset at having failed a first attempt to pass her practical test.
Despite the test failure, she thought she still had a week left on her 12-month overseas licence. But it was only when she passed the test on her second attempt, a fortnight later, that her right to drive unsupervised was restored.
A friend, Margaret Thompson, who intervened with her insurance company, said Ms Zhang was not told she could no longer use her overseas licence after passing the theory test.
She was still unaware of the condition when the testing officer for her practical session allowed her to drive off by herself, after failing her and getting out of her car.
Transport Agency spokesman Andy Knackstedt said overseas drivers who passed their theory tests were given full New Zealand licences, but with a "supervisor condition attached".
"It's not a restricted licence - technically it's a full licence with conditions - that's where I think she got into trouble," he said.
Although the agency produced printed and online material to ensure licence holders were aware of the requirements, it was the responsibility of individuals to understand and comply with those. But as a result of Ms Zhang's case, it would investigate changing driving test application forms and the Road Code to include specific information about the status of overseas documents once New Zealand licences were obtained.
Testing officers were not expected to wait with applicants after tests were completed to ensure they did not drive off without a supervisor, Mr Knackstedt said.
Mrs Thompson said the law should be changed so international documents remained valid until replaced by unconditional New Zealand licences. "They've gone from allowing her on an international licence to drive as a full-fledged licence holder for a year, and suddenly they don't consider her [Ms Zhang] capable of driving unsupervised."
She feared there may be thousands of immigrants in Ms Zhang's situation. But Mrs Thompson said Ms Zhang's insurance company had since proved "very fair and understanding" by reaching an arrangement with her friend which she did not feel at liberty to disclose.