What it boils down to is that she was denied citizenship because she hasn't become "French." Freedom of religion isn't really the issue here. She can speak the language, which is more than I can say about the immigrants in the US, but she doesn't know the laws or customs of the country in which she lives. She's living in a vacuum and, therefore, isn't a member of society. France has a right to withold citizenship from people who aren't really interested in being French and just want to continue living as though they're in another country. When in Rome...uh...Paris...
I just wish the US would adopt such a philosophy instead of letting in anyone who wants our dollars, education, etc., but refuse to learn the language and pay taxes like the rest of us.