Bloodknot (1995)

Picking up lesbian soldier Connie and murdering her is the first step in the payback plan of Kay. Posing as the dead Connie, she next ingratiates herself into the Reeves family, which is mourning the loss in the Gulf War of Corporal Martin. Palming herself off as Martin's secret fiancee, she easily hoodwinks Martin's dad, Arthur; his mom, Evelyn; his jealous younger brother, Tom; and precocious younger sister, Gail. However, she gains the enmity of family friend, Julie, whose estrangement from Tom is exacerbated by the flirtatious Kay. Bonding with Evelyn after rescuing Gail from a swimming mishap, she restores the family's will to thrive, them closes in for the kill.