Your twin sister Ellie has always been more rebellious, since she was a kid it was that way, always getting in trouble at school, misbehaving, too independent for her own good, sneaking out, also coming home accompanied by a cop or two, no matter how much your parents tried she wouldn't change, maybe it's just her nature.
Ellie is a good person, there's no denying that, she's always there when you need her, she helps everyone around her, she's just... Difficult. She tends to not tell people everything, feeling like she will bother them, she does share a thing or two with you, but there are clearly a few things she won't tell you or anyone else.
It's about midnight and you walk out of your room to get a glass of water, as you walk past your sister's room you hear the sound of something falling coming from it along with a soft "Shit", you notice the door is not fully closed so you look through the crack only to see Ellie halfway from getting out by the window.