The cited passenger list gives Selma Rindsberg, age 41, widow, born Berndorf and last residing in Milan, Italy. Her daughter Gertraud K, age 11 is born at Nurnberg. They sailed from Havre 30 March 1939.
Selma gives her closest relative/friend in her country of origin as her Mother-in-law, Mrs. Rindsberg, at Komturci 2, Wurzburg, Germany. Her U.S. destination is given as Bellemead, NJ, where she plans to join her brother Lutz Daniel.
The Social Secuity Death Index gives Selma as born 27 May 1897 and her death as May 1984. User contributed information indicates she died at Jamaica, Queens, NY.
Second husband Walter Hohenstein, per SS Death Index, was born 17 Dec 1908, and died Feb 1987. User contributed information gives place of birth as Vienna, Austria, and death as Floral Park, Nassau, NY.
Gertruad Weinstein according to SS Death Index was born 11 Jun 1927 and died 14 Feb 2009. User data gives her death at Flushing, Queens, NY.
According to the 1940 Census that John already mentioned, in 1935 Selma and Gertraud were living at Bayreuth, Germany and Walter was still in Vienna. (Walter's occupation is given as a chemist).
I think chemist is uncommon enough of an occupation to say the Walter Hohenstein, age 30 and single, chemist, who arrived on the S.S. Champlain that sailed from Southhampton (England) on 16 May 1939. His residence at the time is given as Lausenne, Switzerland. His nearest relative is mother S. Hohenstein of 74 Hasnerstr[aße], Vienna. His destination is given as Paterson, NJ where he will be joining his uncle Hyman Peller of E. 22nd St.
Walter Peter & Selma Hohenstein are both naturalized early in January 1945.
Walter makes frequent trips over to England (and elsewhere) usually on his own - I would presume this is for work. In 1947 he is listed as a chemist on arrival in the U.K. but starting in 1948 he is listed as a "professor of chemistry" or in some records just as a professor.
According to court proceedings in Gertrude Weinstein et al., Appellants, v. Walter P. Hohenstein, Respondent, et al., Defendants [available here] Selma and Walter separated in 1954. This court record also gives a middle name for Selma of 'Sue'.
As to gertrude, Legacy.com reproduced an obit that appeared in the New York Times on 28 July 2015 for Clement Weinstein which says "predeceased by his beloved wife Gertrude, he leaves his loving sister, Ruth..." it continues to name children and grandchildren which I will omit here. The same website also has an obit from the New York Times dated 17 Feb 2009 which says in part "WEINSTEIN--Gertrude, on February 14, 2009. Beloved wife of Clem, devoted mother of..." and again names children and grandchildren. This appears to confirm the user contributed information I listed above.
The impression I get from the various records is that 'Grede' is a nickname for Gertraud (as given on this individuals' website) and that the two profiles, as well as the two husbands named Clement Weinstein should be merged.