Need advice, please help?

I used to be a compulsive liar, and then I realized lying makes me look like a jackass and stopped being so stupid. But when I did, I lied to a girl who ended up becoming my girlfriend and then my best friend. The lies I told her were big lies, and if she ever found out I wasn't telling the truth, I'd be screwed socially for the next two years, because she is coming to my school next year. I cannot tell her the truth, that's not even an option, but continuing to have to lie to her is too much, even though she rarely mentions it. Would it be better to just keep the lie going and continue to be an asshole, or just cut ties with her completely and forget about it, or something else, I don't know, it's been a year since I've met her and it's been eating me up ever since then. Advice please?