I recently became guardian to my younger sister, but she refuses to listen to me.

I am 26, and my sister is 16. Our parents died last year, and I am now my sister's legal guardian. I don't have any kids, and I just don't know how to deal with her most of the time. She's such a nightmare. I seriously don't remember being like that at all when I was her age. Like, I tried to give her a midnight curfew, but she never sticks to it, and when I confront her about it, she goes crazy, starts yelling, swearing at me, saying I have no right to tell her what to do, and that our parents never gave her a curfew (I don't really know what their rules were about that; they always made me be home by 11, but I don't know what they did with her since I wasn't really home that much). She is getting C's and D's in most of her classes, and it's the same type of yelling if I confront her about it. She got a speeding ticket once, and I tried to ground her from her car; it was a literal wrestling match to get the keys from her, and I hid them in my room, but she just came in and looked through my stuff until she found them. I don't know how to deal with a teenager! I don't know how to enforce rules and stuff, especially when she brings up that I'm her brother, not her parent, and that I can't tell her what to do. When our parents were alive, I would always just threaten to tell Mom and Dad on her, but I can't do that, now...she's so insufferable, and I don't know what to do! via /r/Parenting http://ift.tt/2E4lXds