Pansy was the bridge that bind the Order of Phoenix with the rest of Wizarding Britain which was now ruled by Voldemort and his pawns. Pansy was pretending to be a Voldemort loyalist while secretly helping out the Order and doing everything in her power to make this war end. There were a few other Death Eaters working together with the Order, but Pansy was the only one who ever crossed the line to get to Hogwarts and tell them the latest news or warn them of any danger while also doing her job on the other side and making Voldemort believe that the numbers of Order were rapidly declining and that their side will win the war any day now.