I'm afraid I don't have any leads on Laura Pelke.There are a few things I can add, however.
First is that ethnic Germans of that time had a naming convention that is a little different from what we're used to.The first name was either a Saint's name or that of a close friend or family member that was being honored.The actual given or "call" name of the child was the second name.Hence, my grandmother was Henrietta Augusta Pelke, but went by "Augusta."Are you sure you are searching with the correct first name?Genealogy software makes it hard to search in cases like this, because it assumes the first name is the call name of the person.
Second, looking up German/Polish ancestors is difficult because many of the areas that were German Empire prior to 1918 were given to Poland or, after WW II, to Poland and Russia.These included the provences of East Prussia, West Prussia, Posen, Pommerania, Silesia and part of Mechlenburg (basically everything East of the Oder River).At the end of WW II the German populations were either dead or driven into what later became East Germany.As a consequence, almost all of the place names changed.
The places I've looked have given references to Pelkes, Pehlkes and Pelkas in the former West Prussia and Posen, both now parts of northern and western Poland.
Try the following sites for some leads and help with the geography.
If you can find a death certificate for Laura Pelke, it may contain her parents names.Likewise, if you know what church she belonged to in the United States, the particular parish (especially if it is Catholic or Lutheran) may have a record of her (e.g., marriage, death) that would contain her place of birth.