I feel horrible, help with a girl I like so much that won't date me?

So there's this girl I've liked for around 2-3 years. She liked me the first second she saw me when I was at work and she was talking to my co-worker that she's been friends with for a long time. Well the next day or so she went through his phone and found my number and we started talking. After a while I always tell girls (the ones I actually think I like or want to date) that I am an atheist so that I don't waste anymore time if they just can't, I guess handle that or something. So from there we agreed that we just wouldn't bring the subject up (she went to a christian school, now going to christian college and she still doesnt bring it up). So from there we texted and talked on the phone every once in a while for at least a year and a half without hanging out. We've only had 3 or 4 arguments in all. She seemed to me to be the one for me. Just about a month ago, me and my friend that was ( and still is) my co worker went over to her house to chill (first time us hanging out). We laughed and had a great time, watched a movie and we madeout and stuff. Then we started talking a LOT...but then after a few days... she kept asking me for reasons why i like her, i literally was telling her how i did all day. And when i asked her, she just talked about how good i looked, so i asked for reasons other than appearance and she said well...i like you as a friend. My heart stopped, it was the shittiest ive ever felt for a while. I got mad, because it happened a few days after i went to her house, and i thought she was liking me more and more, i never thought that in my life, i could feel used. she told me that it was because i was atheist and that her whole family wouldnt approve. I wouldn't have minded at all to be friends with benefits (what she wanted to be) in the first place if she would have told me that. She goes to Lee Uni now a big christian college and i was going to go for her, and she said if i did we could date. she has money and is the smartest girl i know so she goes about free and i didn't want to bother going and end up in debt. I guess now it just comes down to that we can never be more than friends with benefits, and i just dont think i can do this anymore. just recently shes started talking about her ex and how she kinda loves him and i asked how she was feeling since she was having a bad day the other day and she said "much better, i saw my ex twice in 2 days:)" and i felt more and more saddened. she wants to be back with him and i said just get with him and she said "i cant he has a girlfriend, but they are about to go on a break:)" and she wants to be friends with benefits with me until she gets back with her ex. ive just been feeling empty lately and its harder to talk with her, yet i play out and ive always been there for her. and she told me when we got in that huge argument about how i told her i felt used about all the things she loves about me. and now im just confused and i guess im just needing to vent this out and want advice and opinions. i prob sound like a baby or something but it sucks so bad. i do want her to be happy more than anything but when i think of her in love with another guy like this, it just breaks me down just about.