I don't think it's as much a matter of finding some trick question, as a matter of her coming to understand why humans can't work like that. Anarchy of that kind is based on the idea that, basically, people will care about each other and work for the common good and all, and at least work together well enough to isolate anyone who doesn't play nice like that and is a, you know,
There are very few things that that can't answer _and_ can be packed in a short trick question. The way to dismantle it is to make her understand why humans can't work like that on a large scale, i.e., that that answer is in itself wrong.
I think that at least for me the Revelation Of St Hans

came when reading about Dunbar's number. Essentially anarchy does work in small groups -- as in, below 150 -- just because everyone knows everyone and is in a meaningful relationship with everyone. Above that, well, you need some form of "archy" just because you get a lot of cliques who don't give a rat's ass about each other. And more importantly have no idea what the other groups even want or need.
At any rate, what made it possible at all to rise above the level of 150-people tribes was, basically, inventing some form of "archy" that enforced some kind of working together above the biological limits.
Of course, if you have a proponent of primitive tribal anarchy... well, good luck there.