There is a book entitled Caldwell Parish in Slices by T.H. Wood(s) that has their family information in it. It explains that Mary Catherine's grandparents Jean Baptiste Ferrand (ca. 1768 - ca. 1838) and Mary Catherine Louise Fauveaux (ca. 1770 - ca. 1845) came from France. They had Hypolite and John Alphonse Ferrand. Hypolite was born in France. John was born in Louisiana. The Ferrands came into the U.S. in New Orleans. At some point the brothers moved to north Louisiana to the Caldwell Parish area and acquired land. They had the Synope Plantation. Mary Catherine was Hypolite and Eulalie Etier's daughter.
That's all I have right now. I ordered the book, but it hasn't come in yet. I had a copy checked out from the library, but I've since returned it, so I can't use it as a reference right now. I'll add more if there is any more information on Mary Catherine when the books comes in. I am a descendant of Hypolite's, but not Mary Catherine's, so I wasn't specifically looking for information about her when I had the library's copy of the book.