If Elaine's ancestors came from New East Prussia, the area around Konigsberg, now Kaliningrad, she would have been on the borders of the Suwalki Lomza gubernias in NE Poland which used to be in Lithuania in medieval times, but went through several different ownerships in the 18th and 19th centuries (Prussian, Napoleon, and Russia's Pale of Settlement) and then formed part of the front line in both WW1 and WW2 between Germany and the Allies . in 1919, the northern part of these gubernias returned from Poland to Lithuania. The border changes were very fluid over many centuries and Russia held sway for much of the 19th century in this area.
It was common for those coming from Suwalki Lomza to say they came from Konigsberg/New East Prussia when they went West in the 19th century. All my eight great grandparents came from these gubernias and all of them emigrated to the UK between 1865 and 1875. Some of them said they came from New East Prussia, as likely they were smuggled over the border and likely they sailed across the Baltic from Konigsberg. And their homeland was part of Prussia in their parents' time, but then later on became part of Russia. My ancestors' census and naturalization information say they came from Russian Poland on the whole, because when they arrived Poland was part of the Russian Pale of Settlement.
Depending which DNA provider you go with you get different results - they are not attuned to Jewish DNA and you need more sensitive analysis which can be provided by some specialist DNA providers (I have had this done). On Ancestry (which in my view is the least sensitive), 23andme, FTDNA and My Heritage, I am given wildly different ancestry make ups varying from 100% Ashkenazi to seven eighths Ashkenazi/one eighth Sephardic and to 89% Ashkenazi and 11% Russian/East European. It depends on the reference populations the companies use. And some of the reference populations may self -identify with one country or another, depending who ruled when their families left. Or who rules it today.
I would take most of the DNA results from the big companies with a barge pole as none of them agree with each other. But at the end of the day it is the combination of the paper trail and DNA results that counts. You need to track your family tree by tried and trusted means before trying to match them to DNA.
Jill Whitehead, Surrey, UK