Maybe I am guilty of oversimplifying things. Maybe. But, is there any chance she really doesn't get what is going on? If I were raised in an enviroment where nothing was expected of me, and unless I spent alot of time with other responsible, mature adults/kids, I just wouldn't get it.

So, any chance of a sit-down, non confrontational talk? Maybe, "(insert name), I realize this all must be pretty overwhelming for you. You lost your dad (and mom??), had to move in with me, and things are hectic here with me and my kids. How are you feeling? What can I do to help you (yes, I said to help her, as she is still the younger person, you still the adult)". Maybe there is just a communication issue? Maybe she sees things vastly different? Maybe she doesn't realize what is going on? OR, maybe she is just a manipulative, non-caring, evil person. We do have those in the world today.

But, until you have gotten a sense of where she is from, I can't see how you will know the path to take.

It seems that she has some mental health issues, and I don't seem to be able to move past that. I know this isn't what you want to hear, and I am sorry, but, I feel really, really sorry for her.