I'm going to move onto both sides of the fence here for an attempt at a little perspective.
Your mother is not condemning you, nor is she trying to shove her religion down your throat for the sake of being malicious or a "bible thumping b***h," as I read earlier on. If I had to guess, I'd say she's worried about you. What she believes in, and strongly it seems, is that if you do not believe in God, you will go to Hell. Now, I personally find it understandable to be upset by your choice of lacking belief since, after all, you're her child and she loves you. She's upset, and worried, that you'll burn in Hell because you don't believe. I don't think she's intending to be malicious with her words. I just think she's afraid for you because she loves you. It's an understandable fear, based on her beliefs. Do I think she could handle the situation better? Of course. It's causing friction between the two of you. I don't think she's being malicious, though; I don't think she's saying, "I'm right, you're wrong. Believe or burn in Hell!" I just think she's dreading an afterlife without you.
Now, moving to the other side, you should not have to feign belief in something you truly do not believe in, nor should you be forced to believe in something you truly do not believe in. I don't think you should discuss this since it seems to be a significant issue; if neither side is willing to accept the other, then discussion is pointless. Believe in what you choose, or don't. As an individual, you have the right to believe in something or not. It's your decision. It's not something that needs discussing; it's an area of life that you and she do not have in common. Instead of focusing on it, focus on the areas that you do -- other values and morals. This shouldn't define your relationship with her, so do your best to not let it, and I hope she does the same. Good luck. n u n