I contacted my sources in Russia and Israel about Rosa Pinsky and they have come up with a likely explanation based on their research thus far that is somewhat at odds with what is currently thought about her, but explains her return to Poland after the disaster.
According to my source, Rosa Pinksy was NOT a "Polish-American" - at least not yet at the time. She did not actually live in Burrows Street in New York but was visiting relatives/friends there (and elsewhere), presumably with plans to move herself and her children (who were still in Poland at the time) to the US. So, unlike some sources, she was not 'returning' to the USA on board the Titanic but actually going there, although it may not have been for the first time. Details awaited.
From what I have learned, Rosa Pinsky was born in a small Polish town called Bereznitsa in 1880. Bereznitsa was a 'shtetl' (meaning a birch grove) and most Jewish families is the Russo-Polish region lived in shtetls at the time. There is some evidence that Rosa's parents were upper middle class, probably even wealthy. Rosa grew-up there, attended a good school and eventually got married. Her husband and she moved to Warsaw, presumably in the early 1900s.
We do not yet have information of Rosa's life from the early 1900s to 1912 but she and her husband might have visited the US during that time with the intention of immigrating there. They did have children, one of them a daughter named Leah. Rosa was widowed a few years later (details awaited) and she presumably decided to move to the US with her children after that. That would mean that her voyage alone on board the Titanic was a visit to explore possibilities.
On board the Titanic Rosa shared a Second Class cabin with Ellen Toomey, Bessie Watt and the latter's daughter Bertha. Rosa was rescued on board Lifeboat 9 and upon reaching New York, spent several days recuperating in hospital. She was helped by the American Red Cross but she either changed her mind about exploring settlement in America or circumstances did not work out as planned. Either way, Rosa Pinksy returned to her children and family in Poland soon after recovering.
Rosa and her family moved to Volyn just before WW1; they went through a hard time during the First World War and later especially the Bolshevik Revolution and Polish-Russian hostilities. By 1922 the family fortunes had started to decline due to hostile attitudes of the Bolsheviks towards business people. Volyn suffered a lot due to being in the epicenter of hostilities between Russia and Poland. They were virtually bankrupt by the 1930s but lived quietly for a few years before the Germans invaded in 1939. Oddly enough, despite their Jewish status Rosa and her family appear to have suffered no major hardship through the Nazis themselves. But they and other Jews in the area were especially targeted by Ukranian nationalists and it is believed that Rosa and her family were butchered in 1943 during the Volyn massacre. Rosa is believed to be buried in a mass grave.
Rosa's daughter Leah somehow survived that massacre (details awaited) and later moved and settled down in Israel. She became Leah Grynshpan, presumably after marriage; the surname was anglicized to Grinspan at some stage but it is unknown whether Leah herself moved to the US; her descendants may have done.