The argument of:

"I used to be an atheist like you" people, I just met one today- and I got exciting. Someone with a complete different standpoint to debate with. Yet, when I debated with her today, she was not making very good case about her religion uprising instead targeting the idea of "if you don't convert you will be going to Hell". To tell you the truth, it is kind of insulting. :/

 I don't condemn or threat someone by burning them because they don't believe the same religion as I do.

So, I doubt that the "Once Atheist now Christian" maybe lying about her past- trying to get some false empathy.