I have not read her postings on FB, so can't comment on that, but I believe that the classroom is not the place to be singing or reading about religion, unless it is part of the Curriculum. That certainly IS NOT what I want my tax dollars to be used for. As far as the childrens actions re: the bible and card, I think that the parents should be reprimanded.
I support her, but she should know better as a teacher then to post anything on facebook, it's a public forum. Facebook is not the college age niche it used to be. There are teenagers through retirees on there.