You have this information, right? Well, if you love her, admit it. It goes along with honesty, but you know. Some girls want to be loved, and I'm one of those girls, which is how my boyfriend made me fall in love with him. At first, it wasn't his crooked smile, it wasn't the noises he makes when he yawns "like a kitty." It was the thought of being loved and the prospect of his loyalty that made me love him.
If you know you love her, admit it. If you're shy about it, though, she might find it amusing once she knows to torture you for hours on end until you spill the beans.
Moreover, be loyal. Even if you aren't a thing, then stay by her side. Even if she has someone already, usually she finds it nice to have a male friend by her side. Don't get disappointed over her when she asks for you to help her chase down someone new. Your goal is to make her happy now.