Fresh, welcome to the forum!
I wanted to weigh in on this because I can give some personal insight.
First, Igor is a wise man, and you should listen to him. He's giving some good insight here, as are the others. It is correct, the passage which speaks of the Christian staying if the non-Christian spouse wants it, is speaking far more of the issue that arises if one converts to Christianity rather than one marrying a non-Christian.
Igor said, "It could be that through her, you will see how much having God in your life could mean to you, and just how much truth there actually is in Christianity when you allow the Holy Spirit to show it to you. (Yeah, I know, fat chance you say! But I’ve been surprised by what God can do in a person’s life too many times to ignore the possibility!) So it could actually be God’s will for the two of you to be in each others lives right now."
I agree! My brother came to know the Lord through his relationship with a Christian girl. They've been married 30 years now. And, believe me, he wasn't about to fall for any religious twaddle before he met her. God used her to bring him about. It can happen and does happen all the time.
Now, as for being unequally yoked: It isn't as easy as it sounds. My husband wasn't an atheist when I met him, he believed that Jesus was God, but there were many, many areas where he was just way "out there" when it came to religion. So much so that my entire family exhorted me not to marry him.
I did anyway, because he did believe in Jesus Christ. However, we were nonetheless "unequally yoked" for a large part of our early marriage. And it was hard, very, very hard at times. I will say that God drew my husband closer and closer and now he is a man of God that I am equally yoked with, but it took years and it caused some issues that we are still dealing with the ramifications of.
I truly don't see how it would have worked out if my husband were an atheist. I truly don't, and I'm a pretty fair-minded person.
You see, as a Christian, we believe in a God of love, not One who just wants to suck all the joy out of live, but rather One who wants us to be joy-filled in this life. And, He commands certain things because, in the end, no matter how much we might think otherwise, He knows that it will bring us the most peace and joy. Being unequally yoked in a marriage is not the pathway to peace and joy. Trust me on this.
No matter how much you might think it won't, the disparity in your beliefs about God are going to impact each other. If you continue to remain a staunch atheist, then she will either lose her faith, or leave you (if not in actuality through divorce, then emotionally, which can be just as devastating).
But on the other hand, I do hope that the impact will be that you will know God better. You are obviously deeply in love with this girl, her relationship with God makes her the beautiful woman that you love. Since the two of you are so much in love, spend some time exploring Christianity. Perhaps in time, you two can become one. But, if you truly reject God, then both of you will be better in the long run to separate, as horrible as that sounds.
I'd love for you to talk your girl-friend into coming to the forum as well. I promise that I won't try to split the two of you up! ;) Truly, I'd like to share with her some of the issues I faced with then boyfriend, now hubby of 12 years and how I coped with it. She might find it helpful.