Note the "fueling" of "Nationalism", "committed" atrocities on the German side, while the French side only gets confronted by "wild rumors" and "accusations".
At that time Nationalism was a force for good throughout Europe demanding more egalitarian rights for citizens, democracy and separation of state powers, but also promoting independence of other nations as nationalists of one nation even travelled to other countries to support their Nationalists, for instance to Poland in support of their protests against Tsarist rule.
She leaves out this context, as well as that the French state (throughout being an ancien regime as well as being run by Napoleon) was waging multiple anti-German wars, basically treating the lands to its east like its Hinterland in need of Franconization (E.g. At the end of the 18th century just about 1% of the Elsassians spoke French, and even in 1953 80% of Elasassians were in favor of German speaking public schools).
She also seems to leave out the context, that Bismarck was an aristocrat and thus anything but a nationalist. And since she seems to be in need to see (or letting us see) the word nationalism in todays western liberal meaning, that whole differentiation seems inaccessible to her.
Germany "refrained from ethnic cleansing" (written as if this was some sort of novelty for Germans) because they considered the occupants German. The mild peace-conditions were given by Germany because Bismarck knew that anything else would foster even more French resentment then there already was („Toujours y penser, jamais en parler"), which would then foster more German nationalism, which in turn would hurt his Juncker-Class.