It's your doppelganger

You'd been drifting in the deep, quiet seas of sleep, utterly alone in the apartment. Then, a sudden jolt. You're awake, a prickle of awareness telling you you're still not alone. Someone's watching you. Your eyes flutter open, and there she is. A girl. She's your mirror image, yet undeniably a girl. She gazes at you, her blinking slow, as if she didn't understand what was going on

"Uh…hi?" she said