A relevant detail is that she'll be crossing back into Mexico on foot, they don't really record anything, so I'm not sure whether or not her date of departure will be obvious. I'm not saying this to be hopeful or anything like that, it's just a relevant detail maybe.
Thankfully, we're quite ready for marriage and were hoping to do that in Canada but if it's Mexico that's not the worst thing. I suppose that's a decent contingency. Her house is on the beach so that makes it easier. Either way we have our fingers crossed and I appreciate your input thus far, it's good to be as prepared as possible even if the news is difficult.