I agree with the lying tactic. Don't try and out-logic her, logic has no place in arguments with the super-religious (and your mom certainly sounds it). People her age do not change their opinions easily, and certainly not from the position you're currently in while you are dependent on her.
She'll only take so much backtalk before she starts taking more drastic measures. I don't know your mom, or how stable she is, but drastic measures can involve making your life a living hell until you're 18, and sometimes further than that. There are plenty of 'camps' and 'schools' carefully designed to fix whatever they think is wrong with you, and until you are 18, your rights are more akin to property than person. I attended one such school myself, though not for religious reasons, and believe me, you'll wish you were back at Christian school where you can at least look up whatever you want on the internet at home.
So pretend to be whatever she wants you to be and get used to keeping your secrets under wraps. If keeping secret books is difficult, find information sources on the internet, just about every piece of knowledge known to man can be found there.
Obviously, you'll have to go through the religious motions. Try not to let it bother you, think of it more as a social ritual than a religious thing. Meet people at church, have fun, and enjoy life. Once you've graduated from high school, your options open up quite a bit.
If your mother wants you to go to a Christian college, you might have to go along with it (only if she's helping to foot the bill). There are plenty of colleges that describe themselves as Christian-esque. Find a well rated one that doesn't seem to pander to zealots and you can't go wrong. I went to one myself, and, honestly, I couldn't really point to anything particularly religious about it. More importantly, if you decide to go to college, you can finally get a breath of freedom and really explore what you like.
Of course, if at any point you feel simply overwhelmed by the urge to get something off your chest with your family, sometimes it's better to just get it over with. Better to open up and take the punishment than bottle up all that crippling regret.
Good luck.