This pair are displaying many body language signals of flirting. She has half turned her body to ensure her waist looks smaller. Her hand on his chest is a signal to other females that he belongs to her. She has her pelvis up close against his hip, another indicator that she is interested. Look at his thumb, this is the classic body language give away that he is sexually attracted. He is drawing attention to his groin. Both of them are staring lustfully.