On this particular profile she is listed as the daughter of George Smith so her maiden name would be Smith.
Margarete Smith Born 1911 [location unknown]
Daughter of George A. Smith
If you have questions about Marguerite McManus - maybe you could provide any of the following that you know of and someone can try to help you more.
Dates or approximate dates of her b, m, d.
Locations - Country, city/town of b, m, d.
Names of parents, spouses, siblings, children.
