At the end of the day, the question is really whether the two of you can respect each other if you don't change for the other. Can you respect and love her if she remains a devout Christian? Can she respect and love you with your atheism? Can the two of you come to a consensus about how to raise kids (if you want them at all)?
If the answer to any of them is 'no', then she's not the one. Which sucks and will hurt, but it's better to know now before you're married with a few kids and contemplating divorce.
There are, of course, other mitigating factors, like in-laws, but if you can't have a foundation of trust and respect in your own future household, then none of that matters.
Regarding your actual talk with her, don't do anything dumb like giving her an ultimatum. That's the surefire way to end the relationship whether you want to or not. Instead, talk with her. Explain your doubts and concerns and your love for her. A long term relationship is a partnership. While you feel that atheism is the right choice for you (and that you hope she respects you enough to accept that), you're not going to try to de-convert her because you also respect her choices, even if you don't necessarily agree with them. Couples don't need to agree with each other on everything. They do need to respect each other's positions, communicate openly and truthfully, and ultimately come to an agreement on how things should be run.
Basically, just be aware of your tone and how you frame things. This isn't a hostage negotiation. Talk with her, not to her. Give her time and space to explain her thoughts and feelings. Be calm if possible. And don't be accusatory. If you go in complaining about how weird you think her family is, and how you think her mom is being a bitch, and how you love her despite her theism, you're sunk. Nothing good comes from traveling down the road of "Look at what's wrong with you!"
Beyond that, good luck.
If the answer to any of them is 'no', then she's not the one. Which sucks and will hurt, but it's better to know now before you're married with a few kids and contemplating divorce.
There are, of course, other mitigating factors, like in-laws, but if you can't have a foundation of trust and respect in your own future household, then none of that matters.
Regarding your actual talk with her, don't do anything dumb like giving her an ultimatum. That's the surefire way to end the relationship whether you want to or not. Instead, talk with her. Explain your doubts and concerns and your love for her. A long term relationship is a partnership. While you feel that atheism is the right choice for you (and that you hope she respects you enough to accept that), you're not going to try to de-convert her because you also respect her choices, even if you don't necessarily agree with them. Couples don't need to agree with each other on everything. They do need to respect each other's positions, communicate openly and truthfully, and ultimately come to an agreement on how things should be run.
Basically, just be aware of your tone and how you frame things. This isn't a hostage negotiation. Talk with her, not to her. Give her time and space to explain her thoughts and feelings. Be calm if possible. And don't be accusatory. If you go in complaining about how weird you think her family is, and how you think her mom is being a bitch, and how you love her despite her theism, you're sunk. Nothing good comes from traveling down the road of "Look at what's wrong with you!"
Beyond that, good luck.
"I was thirsty for everything, but blood wasn't my style" - Live, "Voodoo Lady"
