wondering why a Canadian woman would need to go back to the US to process papers...
I apologize for not clarifying. She was living in the US at the time.
People from the U.S. are allowed to come to Germany with no visa whatsoever (a tourist visa is implied) and stay for 90 days. Should you wish to change your status during that time, you are allowed, perfectly legally.
The "no visa whatsoever" thing in itself doesn't make a difference. Mexicans, for example, are also allowed to come to Europe without having to apply for a tourist visa and also stay for a maximum of 90 days. It doesn't matter that Mexico is not included in the so-called "Black List"*, we was told repeatedly that there is absolutely no way to change a tourist visa to the kind of resident permit one gets once married (to a German citizen in my case). I am aware that, for example, US citizens can go from tourist to freelancer (something that not all "White List" citizens can), so that's why I was asking if there's anybody who's done the direct move from tourist to residence specifically via marriage, because the Canadian woman I mentioned couldn't do it either. But hey, maybe her experience was a freak situation. If so, I will humbly stand corrected, and will be more careful next time I reply.
But so far, it still looks to me like it mostly comes down to the town/bureaucrat one has to deal with.