Question

How was Dorothea Schlösser able to live a relatively normal life, despite her Jewish heritage?

Answer 1

The reason was that She had Aryan documents from her father. :) hope this helps.

Answer 2

I believe the answer is: She had Aryan documents from her father

While the nazi treated people from jewish heritage as an 'inferior' humans that  should be eliminated, they treated people with Aryan heritage as the 'superior' race that must be protected.
So, the Aryan documents give a identification among nazi soldiers that Dorothea came from 'superior' race.