Question

who became allegory of the German nation

Answer 1

Similarly, Germania became allegory of German Nation. In visual representation, Germania wears a crown of Oak leaves...

Answer 2

Germania is the right answer.

Germania is the anthropomorphism of the German state or the Germans as a mass, most usually correlated by the Romantic Age and the Revolutions that took place in 1848. As Germania is the personification of the German state, she uses a crown or headdress made of oak leaves for the reason German oak applies for heroism.