Believe me, as an older brother of an obstinate sister that was in foster care during her teens, I know more than I would have liked. I am sorry for being crass. I do understand you try to do what is best for her, and you are right, I don't have the whole situation in front of me. I don't know you, your sister or your situation. But from my perspective, assuming a parenting role is not your place, nor should it be. Be an ear, a shoulder, don't be vindictive, even if you mean to do it out of love.
Its cool.
You're right, I SHOULDN'T be trying to assume a parental role and for all intents and purposes I'd rather NOT cause I have my OWN family to deal with. But lets just say her mom is young and "inexperienced", as well as has 2 other kids from different fathers...so you see where I'm going with this? So my hand is kinda forced because I feel like if I don't do/say anything then it would absolutely be lawless in her house.
Trust, I tried being an ear for her when our dad died but she only gave me what she wanted, and me being a kid her age before and having feelings and emotions all over the place, I do my best not to pry, lest I push her away for trying to be too "nosy" or "overbearing".
But regardless her behaviour is unacceptable cause the bottom line is noone or nothing has did anything to her to cause this, she is just being a complete ass for no reason and its purposeful cause she is selective to whom she acts this way. Crazy thing is she is doing fine in school..which in my opinion makes it worse because to me you truly DO know what you're doing and I feel like I can almost get rid of the "teenage puberty angle". It would be different if she was this way with everyone she comes across and her school life AS WELL as her home life is tumultuous on her behalf.
Anyone as others stated, this thread has definitely gotten off track, so I'm gonna be done talking about this situation after this post. But thanks to all for the advice, listening ear, and feedback on the PS account thing