A name like that isn't too odd for us, more like quaint.. It was common at some point to compose names with a female saint's name, or Marie, and a male name, often that of a close relative or someone you wished to honor. I have a Marie-Antoine, Marie-Théodore and a Marie-Ange not too far in my family line.

Sylvestre is fairly uncommon as first name (I met one, in school) but it's a common family name in Québec, from a common ancestor who also went by the nickname of Champagne (Sylvestre dit Champagne). He came from Troyes in France, around the same time as my Roy ancestor (the branch I'm from adopted rapidly the nickname instead of Roy as family name) Sylvestre got family ties to Jean Nicolet, who first explored Wisconsin (Green Bay, Milwaukee areas). I guess your indian ancestor could have been honouring a French Sylvestre friend by his daughter's name, especially that unless she was born christian, this is the name that was given her after her conversion. A few other early Sylvestres men were coureurs des bois and dealt with Indians, notably near lake Michigan, and some married native women (nearly all families of French descent in Québec have one or many indian ancestors, as unlike the English practice the Nouvelle-France authorities encouraged mixed marriages, as you probably know). One local actress is named Sylvestre and we have this history/genealogy TV series that told the story of her Sylvestre and Nicolet ancestors. One of the early Sylvestres in Nouvelle-France wed a minor relative of the Valois, by the way. That woman is also an ancestor of mine.