Johanna Mestorf was the first "German" female Professor. She was however not German as Germany did not exist; Mrs Mestorf was from the Kingdom of Prussia. Wikipedia has it that Prussia existed from 1701 to 1918 and Mrs Mestorf died in 1903. In the totality of the German speaking world Mrs Mestdorf was prossibly the first female Professor.
Current nationalities and previous nationalities do not match. Trying to understand historic facts from a modern perspective produce a fake perspective.
Not calling Mrs Mestorf German may be problematic for some. But hey is that not what a neutral point of view is about?