First, if she knows you love her she is using you to stroke her ego, which means she most definitely KNOWS you like her. I can say that because I was in her situation.
But I knew my friend never looked at another girl and spent all he's time on me because he liked me. He started insinuating "jokingly" he liked me. I "jokingly" rejected him. I would have to be retarded not to notice he's feelings.
So I broke our friendship.
I slowly started getting further and further away from him, until everything that was left of it, was a simple hello and maybe a fief text messages for our B-days.
I won't lie. It hurt. It hurt me a lot. I was he's friend since childhood, and he was like my own flesh and blood. Loosing him was one of hardest things in my life. After that I felt really alone for a long time. But then he did move on. He met a nice girl and he is dating her now. He stopped focusing on me. Now that I see him with her, I feel happy and even though I did at the beginning, I do not regret my decision. I love him. If he is happy, I am too.
Later I moved on and made new friends. I have girlfriend now that is almost as close to me as he was. But you know what is great about this new friendship? I had to grow and accept her as she did me. I changed a little. And I know that her actions and love are more honest and platonic, not a consequence of infatuation. Not that he's always were, but when they became such, I knew...
So here is a fief things you need to get straight in your head:
First, you are by her side because you love her. The question is whether you like her? Would you be her friend if she was not attractive to you? Hah. Like a person in love could ever answer this question. THAT is what I need you to understand. You can't.
Second, she doesn't love you that way. She never has, she never will. Yo are near her, you are thinking about this confession because you are HOPING. Hope is what drives this whole story. Ditch the hope. When you do, trust me the last thing on your mind will be dating her. You need to stop lying to yourself. You still think you have a chance with her. Deep down, this is true, and you know it.
Third, as long as you are by her side, you will hope. As long as you follow her around, she will have your heart. You can age decades, but if the things don't change there will ALWAYS be something there. When she finds a guy who resents your one sided feelings, she will choose the guy and you will be even more heartbroken. Don't let her stomp on you like this. Trust me she will.
Fourth, if you don't confess and don't seize the day, life will pass you by. The worst of all this is the fact that you will REGRET it. You will regret hesitating, you will regret being led on, you will be bitter about it, and above all you will regret the love life you could have had, had you not chosen this waiting and self pity.
Then move on. You can try to stay friends, but know that one of you will soon end this charade of a friendship.