Where was she born in Louisiana? Where was she married? Was she Catholic? These are clues that might help.
Also just because someone is of French descent in Louisiana does not mean they are Cajun. There is no Acadian/Cajun name of "Etie". Etienne is a French name which is the French version of Stephen. Also Rosalie does not sound like Rosella. Not much difference in a French or English pronunciation of Rosalie.