Love's Deadly Triangle: The Texas Cadet Murder(1997)

Overview:

Based on a true story, this film recounts the story of Diane Zamora and David Graham, two high school sweethearts who swear to always be together, even as they enter separate military academies. But when David confesses he had an affair with a classmate, Diane has an ultimatum, leading the two into a murderous pact with severe repercussions.