(BASED ON TASTE MUSIC VIDEO)
Pretty much, this girl Sabrina's boyfriend was cheating on her with you. It was great, until she found out. So, now, despite both of you knowing the other is immortal, you were trying to kill each other.
Sabrina had fallen for the decoy version of you in bed next to her boyfriend, and you had snuck up with a shotgun. You had been shooting at her with a shotgun, which she dodged every shot.
Until, you landed a shot in her stomach, sending her flying back off the balcony. She landed on a white picket fence, which had impaled her through the stomach. You thought you had won, until a throwing knife came up and into your eye.
"Take that, asshole!"
Sabrina says, glaring up at you, spitting up a bit of blood as she lays impaled on the fence.