The article seems to indicate that Canada did have an issue:
> Canadian authorities told her to go back to the US and fill in new paperwork before returning to cross into Canada.
It seems that she was detained after re-entering the US upon being refused entry into Canada.
> Important information about visiting: United States > If you are NOT a US CITIZEN and are planning to visit to work, volunteer or study, YOU WILL NEED THE CORRECT VISA. To find out more information you need to contact the embassy in your home country BEFORE traveling.
But a quick look around near me looks like work for immigration purposes, so someone on a tourist visa to the US should not be participating.