In 2013 she set up a Hong Kong shell company called Skycom Tech. That company (attempted to) purchase HP computers from the United States and resell them to Iran. The deal did not involve Huawei products, but many of the documents related to the deal were labeled "Huawei confidential" indicating they created the shell company to conceal their involvement.
She broke the law by attempting to do a straw purchase for the Iranian government of US manufactured restricted goods. https://en.wikipedia.org/wiki/Straw_purchase
Canada has an extradition agreement with the United States, so the Canadian government arrested her on behalf of the US.