The game was tied at 56 when Bell-Haynes, who had two points at the half, made four straight free throws to put the Catamounts up for good and hit a 3-pointer that made it 65-57 at the 3:37 mark. Twice the Saints made a pair of free throws but each time Bell-Haynes answered with a basket.
Kurt Steidl added 15 points for Vermont (7-7), which went 24 of 31 from the foul line and made 7 of 13 from the 3-point line.
Lavon Long led the Saints (8-5), who were 13 of 23 from the foul line, with 13 points and 10 rebounds. Leading scorer Marquis Russell (17.3), a 55 percent shooter from 3-point range, missed the game with a foot injury and could be lost for the season.
Siena led 36-33 at the half.