Family Update

My mother read the letter I wrote to my family concerning my atheism. She was very impressed by it, so much so she suggested I look into ghost writing. (I dare say she is biased though...lol) My grandmother on the other-hand, refuses to read the letter. "Too Blasphemous" is what she said to my mother. She is choosing to not acknowledge the letter.
She is in denial about the letter and I can only speculate as to why. So far no one else has read it either in the family, not because of refusal but because of lack of opportunity.

I am looking forward to my cousin's response/reaction. In fact his reaction is of significant importance and interested to me. He has been a major role model and big brother figure in my life. For this reason I value his opinions greatly.
Though all of this sparked an interesting conversation with my mother. She still claims christianity as her religion. The conversation was about believe and what was of particular interest to me had been when my mother stated, "You can't change fifty years of someone's belief." To which I replied, "Well, what do you believe?"
"That the bible is true." She replied. "How do you know it's true?" I inquired.
Without hesitation she responded, "Because god said it's true." Of course, I asked, "How do you know god said it's true?"
"He said it was true in the beginning." was the reply I received.

"How do you know what he said in the beginning?" I asked her.

She replied, "Because the bible says so."

I then said, "So you believe the bible because the bible says it's true?" There was a few moments of silence, 10-15 seconds, after which she replied with, "yeah..."

So maybe my mother isn't the closet atheist I once believed her to be, but I definitely see doubt in her. I know my grandmother will believe until the day she passes and that she probably needs this belief to get through each day. My mother does not. My Mother is far from a fundamentalist.

I already see doubts in her, and I know that she does ot need these irrational beliefs. I just don't know hot to convey this to her. Not in a way she will not take offense to. Suggestions would be immensely appreciated.
This woman birthed me on March 4th, 1985, I literally owe her my life. Against all odds, as a single woman, she had me. Even though her mother, a fundamentalist Pentecostal, was urging her to abort.
She deserves to live without the oppression of religion. How would, or should, one go about this delicate situation?

What would you do?