As a US citizen, I go to my company's Canadian office every so often. I have no issues saying it's for business -- the first time ever I was a noob and was asked to park and go inside for more questioning but once I clarified that my company is US HQ'd, that I was just there for meetings (not actual work?), and that I'm not a manager everything was swell. I later learned actual managers at my company never reveal they're a manager, or at least not over anyone they're going to meet with.

The other thing about volunteering extra information is it can come back to bite you if you're not consistent next time, so I also try being as vague but still truthful as possible. If I was visiting anywhere else but Canada, though, I wouldn't have any problems skipping the whole drama with "I'm traveling for a vacation" and "nope, not meeting anyone I know" regardless of whether that is true or not.

Border crossing is basically a hazing ritual in a lot of places, and while I agree with GP's "this was her mistake" it really is dumb we all have to put up with the hazing. Kind of like not bribing a cop in [insert south american nation here] who is giving you trouble, or bribing him with way too much money. Some people just don't get that there are dumb, sucky customs where not following them (or trying to follow what they think is the most honest or rational process) is a mistake and complaining about the mistake after the fact won't solve anything.