Of what nationality is Marguerite Ledoux? Why do the Sargents call her Maggie?

Marguerite Ledoux is of French nationality, having come to America from France with her uncle and grandmother some time before the beginning of the novel. The Sargents call her Maggie because there is a great deal of animosity against those of French nationality at the time due to war between England and France. The Sargents find it more comfortable to call her by a modified name for this reason as well as ease of pronunciation.