I had to give her credit for putting it out there. I am not religious, do not believe in God, and I usually appreciate when people keep their beliefs to themselves. Yet, being a person who holds other very strong beliefs, I sometimes want to risk a friendship by taking a stand. So I am not offended by her action - it wasn't personal, anyway, I am sure her letter was a mail-merge document.
I was offended when I learned that someone else in the department was praying for me so I wouldn't go to Hell.