Replying to Need Some Advice from the ladies

So I've had basically a crush on a girl for... well... ever. Finally last fall I decided that if she never knew how I felt, I was the only one to blame for my problems. I worked up the courage and asked her out straight up in person. She told me she really didn't know me that well. I was just like, If your not comfortable with it its OK I just wanted to know if you would. So anyway, we didnt go out, or really converse much after that i think mostly because of the awkwardness of the whole thing. There still is a hint of the that awkardness now, over half a year later, but at least its nothing like it was before. With Graduation looming I fear not seeing her anymore without much closure. I know there is not much I can do If she doesnt want to go out, but how can i tell her or make her feel like everything is cool and that I would like to be as good of friends as she wants to be.