"Aennelein von Torgau": Torgau is a city in Saxony, far away from East Prussia. The tune (incipit) is not the same as in Alberti's book, the first name has a different number of syllables - in one word: no.

Also, "Anke van Tharaw" is not her name; it must be translated "Annie from Tharau".

The book by Müller-Blattau is obviously pure ideology, as often found in dictatorships or in countries with a strong national ideology (i.e. in many countries, even if appearing as democracies). As a rule, never trust a book titled something like "History of *** Music" where *** is an ethnicity or religion etc. --

I found a source of the "Dach in love" legend: Wilhelm Müller ("Winterreise") reports it in 1823 and clearly remarks "Man erzählt über die Entstehung dieses Liedchens Folgendes: Dach liebte die Pfarrtochter von Tharau ..." In short: pure romantic invention by people who did not even bother to read the lyrics carefully.