I too, thought Chaloff was Jewish, so maybe both our memories are playing tricks on us.
Probably Russian, not Russian-Jewish. Also, Margaret is the name of a saint -- not that all Margarets were or are now named after the saint, but back then I believe that many Margarets were. In any case, not too many Jewish girls named Margaret, at least not of Margaret Chaloff's vintage. Also, now that I think of it, not too many Jewish boys named Serge either.
According to the booklet in the Mosaic set, she was of English descent. Margaret of course was not an uncommon name for Anglos of that vintage.