If she pulls you into her arms or says "kiss me!" that's a pretty good clue. If you're uncertain, see how she reacts when you say "I'd like to kiss you". If you don't want to be as direct as that, compliment her on the color or the shape of her lips. Saying "kiss me!" and waiting what happens is also a good way to find out.
if she looks into your face in a different way than before, that could be a clue.
if she wants you to kiss her, it should be pretty natural.