I Need To Apologize

I really want to tell her I am sorry. Ever since our last conversation, I have felt like a really horrible person. It wasn't even part of the conversation and she probably doesn't think anything of it. It was just during the conversation I had a sudden realization of what I was doing this entire time and it just isn't right. I'm scared to apologize to her this time though. I am nervous that me apologizing is going to end up making her feel bad too. She has nothing to feel bad for at all but I still feel that she will. I can't give any detail about what I'm talking about though.
I just don't know what to do, it's like one of those things that could be left unsaid and something she would not even think about but it's really eating me.
I hope she really knows what she means to me..