"I was granted my trade Nafta work visa, which allows Canadian and Mexican citizens to work in the US in specific professional occupations, on my second attempt... I had gone to the San Diego border the second time to apply."
So: she tried to get a work visa, was denied. Hired a San Diego lawyer, entered from Mexico, got her visa granted. Went home, tried to enter the country again, got her visa revoked and told to speak to a consulate. Then tried to enter again from Mexico, at that point she got detained.
Maybe all this could've been avoided if she did the visa paperwork through the consulate, like she was told to do, instead of showing up at a land crossing after her visa was revoked? A land crossing from a country she has no status in (Mexico), especially. Presumably she was detained because they couldn't just turn her around back into Mexico.