Agree with Brary!
It's ok to feel attached to a girl you have feelings for. Even if you're not in love. Her being cute, nice to be with and good looking, might be enough to want to have her by your side constantly.
I know that feeling well. In my case, I'm not in love and Don't want serious relationship, I just find the girl pretty, nice to be with and well, some one whos company I enjoy. But yes, at times i feel attached to her, like i want to see her more and more, for no romantic reason

(although in my case, i kinda lost the oportunity to K close and take it further, so Im pretty much done and I dont regret what I did, I learned)
If you really want a relationship with her, you can always try being oldschool, being romantic in an old fashion. Some girls like that.
But, Another thought. Don't make her responsible for your feelings. Leting her know how you feel about her and what your romantic intentions are, is not going to make her come close to you. Instead it's only going to make her feel as carrying an emotional burden she might not be wishing to carry for the time being. Consider that. Even if she does like you, she might not want to have emotional responsabilities with you (or anyone else).
If you think shes in control now because she thinks SHE HAS YOU, and does nothing. Then she might not apreciate you enough. Is that ok with you? Wishing to be with a girl that might not care about your feelings, a girl that might even try to take advantage of it?
On the other hand, one thing that I've learned recently is: Whatever you feel, go for it, dont hesitate much and dont take too long, cuz sometimes you only get one shot to make it right.
If you want to tell her, think of the propper, most clever way to do so and Do it!!
Good luck man