Let me see if I have these relationships right – Harriett95320 is a child of Dorothy, and Dorothy is a child of Nancy Gay and a male Greenberg. If the male Greenberg is David Greenberg, then Dorothy was a half-sister to Shoshana, Moshe, and Chaim. This would make the DNA-tested grandchildren of Shoshana, Moshe and Chaim the half 1st cousins once-removed to Harriett95320. It is only the grandchildren who matter, since they are the closest generation to Harriett95320.
What you should look at are the number of centimorgans (cM) that each of the Greenberg grandchildren share with Harriett95320. On AncestryDNA, you click on the line for a DNA match that says ‘X cM / Y% shared DNA’ (where X and Y are numbers). That will open up to a new window, which will show the following information:

The amount of shared DNA and the longest segment will give an indication of how closely Harriett95320 and the grandchildren of Shoshana, Moshe, and Chaim are related.
Finding if David Greenberg had a brother - that would be done by looking through records for this particular Greenberg family, to see if a son shows up in an early census, prior to 1917. It is also possible that there is a family tree on Ancestry that shows if this David Greenberg had a brother.
San Bernardino is close to Los Angeles, so I would look for a male Greenberg who had been in the Los Angeles area in 1917, about the time that Dorothy was conceived. This NPE event might be due to a long term affair, a short affair, a one-night stand, or even the remote possibility of a non-consensual act. Regardless, no one would have thought it strange that the married woman Nancy Gay had another baby. And it is possible that the male Greenberg did not know that he fathered a child.
If this Greenberg family has no connection to Los Angeles, it could be that the male Greenberg was there for school, or business, or even something connected to the military, since the draft for men to enter the US Armed Forces to fight in WW I had already begun in 1917.
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Michele Lock
Lak/Lok/Liak/Lock and Kalon/Kolon in Zagare/Joniskis/Gruzdziai, Lithuania
Lak/Lok/Liak/Lock in Plunge/Telsiai in Lithuania
Rabinowitz in Papile, Lithuania and Riga, Latvia
Trisinsky/Trushinsky/Sturisky and Leybman in Dotnuva, Lithuania
Olitsky in Alytus, Suwalki, Poland/Lithuania
Gutman/Goodman in Czestochowa, Poland
Lavine/Lev/Lew in Trenton, New Jersey and Lida/Vilna gub., Belarus