FYI, here are some facts about this apparently accidental border crossing. I saw the woman interviewed on the news and got the feeling she was telling the truth but obviously I can’t be sure. But here’s what I know ...
She was jogging on a beach at White Rock (B.C.) which starts out quite busy but if you jog east for about a half mile it gets deserted. It is not really close to the highway, border crossing points and the Peace Arch and if you were looking more at the view over the water you might not notice those. There is a train track that runs between the beach and the highway. Also, the U.S. customs are actually about a half mile into the U.S.A. so she might not have even seen all of that before the agents picked her up.
I can believe that somebody from France who had never been to White Rock before might have no idea that they were close to a border. Apparently there are just small and rather unobtrusive signs informing anyone that they are approaching a border. Anyone who lives in the area would know this and not need a sign to tell them because the beach ends just about where the border hits the bay (and the shore then curves south into WA).
She probably had no idea that she had jogged across the border. But like I say, no way of knowing for sure.
She should have brought children. My family and I crossed that border and were asked to step inside for questions. Our three young children started climbing the walls. We were free to go very quickly.