Lewis & Short

adversātrix (archaic advor-), īcis, f. [adversator], a female antagonist or adversary (in Plaut. and Ter., and then again in Tert.): nunc assentatrix, dudum advorsatrix, Plaut. Most. 1, 3, 100; Ter. Heaut. 5, 3, 4; Tert. de Anim. 31: quin tu in ea re mihi fueris advorsatrix.