Respect her and her will.. How about that?
I'm guessing you're trying to say you expected more, and now you want to "over-ride" her decision..
Try spinning it around: What if a girl was hitting on you and you liked her but just not in "that way". What if she kept persisting and was constantly trying to find ways to change your mind?
I bet you would soon get a bit bored of that.
My advice would be to not try too hard or you will seem desperate. Play it cool, turn your attention to other girls that actually feel the same about you, try to relax and have fun, be fun to be around, charming and confident.
Those are the attributes that will get you noticed by whoever.