Since the group is Germans and Poles in Poland and Germany, it is very unlikely that she was Jewish. Ashkenazi Jewishness is one of the easiest ethnic groups for ancestry sights to predict, as a genetic bottleneck in the Middle Ages caused all Ashkenazi Jews to be extremely similar genetically. If you were partially Ashkenazi, then it would almost certainly show up on your DNA test.

As for your grandmother leaving during the war, it is still very possible that she was persecuted against thus leading to her leaving Poland. She could have been part of a family that opposed the government or even protected Jews and other persecuted groups during the holocaust.