Nay! Nay! Surely thou must “play it cool”, dropping the most subtle of hints (and waiting upon their return) until it comes upon her that thou might likest her. And then, when thou art watching a movie (or perhaps some other activity as thou sees fit) together, thou makest the move. Put thine arm around her! Let thy love spring forth and become known! Surely, if she doth not resist or become uncomfortable, she doth like you back.
(in theory of course. I’ve never gotten past the “subtle hints” step)