I feel the same way you are about rude kids, regardless of their age, if they are relations, etc.
I think if it's your house - it's your rules. And any visitors to your house should show respect - to you, your family and your household items. That being said, I think you owe it to yourself and your sister to have a talk with her BEFORE you start standing your ground. In essence, you are changing how you are going to behave.
I would expect her to get upset and defensive...so you may want to talk with her in person, so she can't just hang up on you.
I wouldn't bring up anything about her daughter being a single child or condeming her parenting. I would simply say that "you've noticed" that her daughter isn't treating you or your family respectfully. That you understand that she's a teenager and all, but that you have an expectation of a minimum level of respect.
Give your sister a chance to absorb it, get defensive, etc. and don't say anything. Just listen to her. Let her "vent" and don't feel the need to defend yourself, your beliefs, etc.
Once your sister is done. Be clear, that any visitors to your house are expected to be respectful to you and your family and that you are not singling out her child.
All that said, perhaps you are right. Perhaps her daughter is at that "rude awakening" point. Perhaps she's at that awkward teenager stage where she wants to be treated like an "adult" - do what she wants, say what she wants, etc. And that's all fine. Then maybe she needs to also deal with the consequences of her behavior - having strangers, or other adult family members telling her when she's acting inappropriately.