Riggs turned in an 11:45 to help the Lady Texans place fifth with 147 points.
Jasmine Boutte placed 32nd in 12:42, Malisa Lewis 39th in 12:51, Chelsea Reza 46th in 12:59, Caren Stuebe 49th in 13:00, Victoria Rasmussen 55th in 13:13 and Heather Patterson 66th in 13:39.
With a pair of top 10 finishes, Northwest boys secured sixth place at Saturday's meet.
Troy Taylor was ninth and Brandon Steed 10th with times of 16:24 and 16:27, respectively.
They raced in the elite division, scoring 166 points, just shy of fifth which was at 163. Flower Mound won with 61.
Northwest took the fourth spot in the varsity division with 112 points, led by Tate Hunton in 12th with an 18:07. Mansfield won with 55 points.
Also placing in the elite standings were Stephen Johnson in 28th with a 17:14, Josh Dunn 56th in 17:49, Jared Ward 63rd in 17:57, Nick Fowler 78th in 18:32 and Brian Cooper 84th in 18:40.
David Piper placed 18th in the varsity race in 18:22, David Daunford 24th in 18:32, Connor McDonald 33rd in 18:51, James McCann 34th in 18:53, Brady Sooter 48th in 19:30 and Ashton Shelton 64th in 20:26.
