She gives you s_xual compliments: She doesn’t mention your new shirt, but rather how great your chest looks. She doesn’t talk about your new pants, but rather how round your butt looks in them. When she compliments your body parts rather than your clothes, perhaps that’s because she wishes she were your garments.
She watches your lips: In most cases, when people engage in conversation, they look in each other’s eyes when they speak.
If she constantly stares at your mouth, however, it’s very possible that she’s longing for a little something something from that area of your face.