Mary Konye disguised herself with a veil and attacked Naomi Oni in the early hours of Dec. 30, 2012, leaving her with disfiguring burns on her face, a hand and a thigh.
Police and prosecutors had said Konye was jealous of her friend's looks and spent months hatching a plan for the attack following a trivial argument. Both women are 22.
Judge David Radford told Konye on Friday her "deliberate" and "wicked act" had been devastating to Oni in his sentencing at a London court.
"This careful, premeditated criminality was planned against a person who reasonably believed you were a true friend," Radford told Konye. "Her friendship had been so wilfully betrayed by you."