St. Louis remained unbeaten in the Atlantic-10 Conference, limiting the Spiders to 20 field goals and 31 percent shooting.
The Billikens raced to a 42-21 halftime advantage. Jett scored 21 points and was backed up by 15 points and 10 rebounds from Dwyane Evans.
It was the 13th straight win for St. Louis (19-2, 6-0 A-10). The Billikens' last loss came against No. 3 Wichita State on Dec. 1.
Kendall Anthony scored 14 points for the Spiders (14-7, 4-2 A-10).