The Wildcats (20-3, 9-2) are the sole leader of the Pac-10 in their best regular season in the program's history.
Arizona has won six straight, and eight of the past nine. Washington State (4-17, 1-10) has lost 12 of its last 13 games.
The Wildcats jumped on Washington State early as Pickney scored Arizona's first seven points. She finished by making 10 of 13 shots.
Monika Crank added 10 points for the Wildcats.
Yvonne Volkman, Jennifer Kerns and Alison Eldridge each had eight points to lead Washington State.
Pickney, who scored 13 first half points, picked up where she left off in the second half by scoring the first basket, and then sparked a 21-3 outburst to pull Arizona ahead by 39 points.
Pickney continually turned offensive rebounds into points, while her teammates hounded the Cougars defensively.
Washington State tied the game at 11 on a three-pointer from Kerns. Arizona scored the next 10 points as Felecity Willis started the surge with a three-pointer. Angela Lackey added a short jumper, before Julie Brase hit a three and Tatum Brown connected on a spinning move in the lane.
The Cougars could never get any closer than eight as Arizona took a 36-22 halftime lead.