Atheism vs. Christianity?

Lately, I've been having some controversy going on between my sister and I, she a Christian, I an Atheist. She's always there to throw some sort of snide remark about how "negative" my perspective on life was without God and if I would just "open my heart to God" I would be happier. Listen, I was a Theist for many years before I became agnostic towards God, and I really have tried to open up to him, and I have searched for him, and I have confided in him, as if I were to confide in a diary, yet, I get nothing in return and I find no evidence of there being anyone even listening to me in the first place. Then whenever I bring up the comment of "I don't see any evidence..." she comes out and remarks "Well, there isn't 'supposed' to be proof, or evidence, or the sort. You see, that's the whole idea. The idea is to have 'faith' in God, and to 'believe'. To be a true Theist means to keep driving on relying only on blind faith, and that is what truly makes you strong. Logic is only an excuse of you Atheists to smite Christians and their beliefs!" Really?? Are you serious?? How am I supposed to confide in some dude I don't even know, let alone, even know if he's ACTUALLY THERE, when I have REAL friends and family to confide in? If anything, get a journal to write in! Obviously, her logic behind her argument is unstable, but I suppose that LOGIC really has nothing to do with it at all, and that I'm just being a 'weak non-believer' or whatever else she may say about Atheists. I am just not sure how to respond to that without completely offending her (she is very easy to offend!) and I would like to know your controversy on the subject. And yes, I am aware that God may be the only remaining alternative for those who have ultimately "lost everything" but in all honesty, sometimes I tend to be more lenient to the belief that faith is just an excuse to hide yourself from the reality of the truth. But then again, that is just a theory. Honestly though, I sometimes think that most Christians are the ones who are living in the dark. Anyway, please help me out by responding to this question, I'd like to know what you guys think about this entire mess. Thank you, in advance. Oh, and by the way, before you ignorant trolls start nitpicking certain aspects of this question that I may have misconstrued or looked over, etc., please be aware that I am merely fourteen years of age and my sister is only twelve. We both have our whole lives ahead of us, and I'd like to hear the opinions of some clear, educated, respectful, intelligent, responsible, and of course, experienced people. Once again, thank you for your time (please excuse the length of this passage, I was rather furious with my sister while typing it up). Please Respond ASAP!! x)