Second-seeded Shenandoah (11-7) led 7-2 following a Samantha Donaghy free position goal with 5:36 remaining in the first half, but could only watch as the high-powered GC offense came to life.
The third-seeded Quakers (12-6) pulled themselves back into it by scoring four of the final six goals of the first and then took control following the halftime break.
GC reeled off 10 straight from the 21:58 to 1:04 marks to turn its 10-6 deficit into a 16-10 lead.
Bereit, who had three goals for SU, provided the final margin of victory with an unassisted tally 13 seconds before the final horn.
Guilford rallied for the victory by dominating possession in the second – the Quakers won nine of 12 second-half draws after seeing the Hornets win 10 of 15 in the opening stanza and scooped up 11 of 16 second-half groundballs.
GC also took 19 of the 27 second-half shots.
Shenandoah goalkeeper Ashley Cross had eight of her 12 saves in the second.
Sisson paced the hosts with five goals and two assists for seven points with Bereit adding four goals.
Sisson finishes her career as the program's all-time leader in goals, assists, points and draw controls.
Cross finishes her career as the program's all-time leader in saves and wins.
The Class of 2014 finished its career with 48 wins and played in two conference championship contests.
The 2015 schedule will be announced this summer.