Your own personal well being is of the utmost importance, it might feel as if you're hiding who you are from your family by not discussing this with your parents, but you have an awful lot to lose if you were to be disowned.
I would suggest to find a community (such as ThinkAtheist) to discuss the troubles that you have, I'm sure that many people can give you support and comfort that your parents can't give you.
Personally, if I were you I would wait till you're less dependent on your parents for financial support to come out of whatever closet you're hiding in. It's a pity that you feel that you can't be who you are around your family, whether it is true or not that you might not be able to, the feeling that you can't does seem to me to imply that you fear that your mom is basically a bigger supporter of baby Jeebus then her own baby (you)?
I wish you the best, both in family and in love. You're young, you are finding out what it means to be "Becca", you can hide who you are from your family, but I would recommend to find people to talk about your feelings so that you don't have to hide to yourself who you are. Expressing how you feel and think are vital to your development, I do hope that ThinkAtheist can help you by providing you with a sense of community.
Has she ever discovered some friend of hers was not of the right religion? If not atheist, then some different sect, maybe very different, or perhaps agnostic?
If so what was her reaction? It will be worse when it's her daughter and it's atheism, not just her friend Katie being a Mormon. If the reaction is bad, she might let the blood relationship overrule her desire to disapprove violently. But I would not bet on it. Atheism is way beyond the pale for many religious people.
Even if she did decide not to disown/shun you, then you can expect attempts to evangelize you for the rest of your life.
Lesson for life: Religion causes segregation and discrimination.
I agree with your decision not to come out until you move out. I haven't officially come out to my parents, and I'm 32. I think they know, because of the opinions I have about related topics, but I don't see any point to sitting them down and saying "I'm an atheist".
Love your family, and when they talk about their silly beliefs, laugh at them silently, but love them all the same. It's a shame you can't expect them to laugh it off if you came out, but we all put up with a lot of crap when it comes to family.
I am going to tell you what I told my younger brother when he came out to me--
Don't tell your mom until you are able to live on your own.
There is always a chance that she will be accepting and kind, but it's also possible that your life will be made a living hell for the next few years. It's a shame that you have to do things this way, and that you can't be honest about who you are right now. Luckily, you have access to supportive communities of people elsewhere. I hope this will help you get through until a time when you are able to come out to your mom, and I hope she accepts and loves you for who you are.
You have an entire website full of people who see eye to eye with you. From the statement your mother made, I am going to assume that she is rather right wing and conservative. When you are 16 you are sort of dependent on your parents for support, shelter, food, etc. Sometimes a parent will abuse this and make it seem like they "own" you. I understand that this can be extremely frustrating. I have been in a similar situation, but trust me it will get better. If you cannot come out to your family, find a friend that you can trust with anything and talk to them. Having an outlet can be very relieving. I understand that you object to your families beliefs, but why? Get a notebook, or an online blog, and investigate all the beliefs and think about why you object to them. This too can be quite liberating, especially when people comment and agree with you, or give you more information. Learning, although difficult, is liberating and gratifying. Knowledge is power.
Good Luck to you!
There's no reason why you should tell anyone at all even after you move out. It's not important
I wouldnt say anything about it. At 16 you are a young adult and now you will be forming your own world view and your going to change it a million times.
Dont completely close your mind from the modern Christian message either because it really has some great instruction that fits everyone.
Take the good things and discard the nonsense because Atheists can be better Christians than Christians.
My version of that is "Dont Be an Asshole"
All the Best.
I think most kids growing up aren't "really" Christians, they just go with it as you did. At some point or another they start to think about it more deeply and stop just going with it and start exploring on their own. That's normal, and a good thing, as long as you keep exploring. Where you are now, as a young atheist, is fine. Your understanding will continue to change with time. Be open to that.
The first rule is that your parents love you, and always want the best for you. Understand that, and love them for that.
The second rule is that your parents won't always understand or accept what's best for you; like all of us, they are a product of their experiences and they want to use those experiences to steer you where they think you need to go. That can create a lot of conflict with teenagers your age and their parents, if you (and they) let it. Understand that, and be patient with it.
I think a good rule is that when we are guests under another's roof, we respect their practices. I'm a Catholic, but this past week as a guest with Jewish friends, I participated in Passover. I have Islamic friends, and am supportive of their practice during Ramadan. I have atheist friends, and when under their roof I am open to and supportive of their philosophy. That's just being a good guest. In the years ahead, you will have friends of all stripes, and be invited to weddings in churches and synagogues and courthouses and fields. You go and participate not because you believe in their church, but because they are your friends.
So sure, while you are at home, continue as a good guest, because you care about your family. Go to church and participate, just as an act of kindness.
At the same time, it's probably not a good thing to be dishonest. Don't pretend to be pious. If at some point if you feel the time is right to let family or friends know you have doubts, that's an OK thing. I don't think it's something you should throw in their face, but if there's a time when it seems right to share that's fine. Gently.
Accept the fact that parents and family will worry about you, and be annoying at times, and it may take time for them to adjust their thinking. Be patient and understanding.
Find good people to talk to. Atheists and religious, both. Build your own network of support. We all need that. Hopefully many here can help, but look especially for "live" friends for your network as well.