Faith may be in the lower part of the Top 100, but if you were to aggregate names by spelling,
Faith actually falls out of the Top 100 (according to namenerds.com) so I don't think it's all that common.
Faith would probably be the only girl in her class with that name but if she isn't, oh well.
I suppose
Faith is a religious name, but you can have
Faith in anything so it doesn't *have* to be religious. I think it's a sweet and gentle name myself, as well as being a lovely concept.