Despite her efforts at maintaining calm composure and control, it's clear that his random movements, and unpredictable teasing are throwing her for a loop; by the time he's pressing himself against her slit, she's shaking, and clearly very close to begging for him to take her... but manages to maintain her calm, although the thought of his tongue down there sends a new shiver down her spine. Her body's betraying more of her interest than the rest of her, however, as she's clearly extremely aroused, and anticipating him.