Somehow Granger got herself to where her back was to his chest as they continued their dance.  She took his hand, placed it on her waist, right where the dress was tightest.  Draco held his breath for fear that if he released it, everyone would see how her touch sent a shiver through him.  She was only there for a moment, long enough for Draco to know it was intentional and short enough for Pansy and Theo to be distracted by each other and the muggles.