Has Beeattitudes

Yes. Remember that you are the adult in the situation. (One of my dad's favorite lines to use, by the way...) You have no reason to be arguing with a six year old. If there's a problem that needs to be addressed, and you are not successful addressing it with the child, you take it to the parents and recruit their help. If that isn't working, ignore it and/or look for a new place to live because they aren't respecting your needs for peace in the home you are sharing. Good luck.

A 6 year old shouldn't arguing with an adult, especially their aunt. Sounds like mom & dad need to teach her some respect.

Don't argue with a 6 year old. Just avoid her and be firm in your voice if she is being innapropriate, otherwise it's her parents business. Perhaps she is feeling the stress of you living with her too1

Kids will argue if there is an argument to be had...you are the adult so there should be no argument with a 6 year old. She may be "bratty", she may not be completely respectful of you but her parents should address this and if they are not, then maybe you, as the aunt can be firm and let her know that she is being unreasonable and you will not accept this tone, behavior etc from her as her aunt. I am also unsure as to the living situation but sometimes kids get irritated (just like adults) when their "space" is invaded. I am not saying this is what is happening I am simply saying that she may be acting out because she sees you as another sibling since it is her parents home and you are living (as she sees it) as another dependent. Once again, I am not saying you are....children are not always aware of the adult world of paying room rent etc., NOR should they be. However, maybe a little bit of concern for the relationship expressed to your sister in law will help your relationship with your niece improve.

She's only 6. I don't understand arguing with a 6 year old. Maybe you should just avoid her and let her parents parent her.

Oh yes, that age old...I am fighting with a 6 year old. It is simple, love her in all her wise-ness, in all her child-ness and all her fussy-ness...she is 6 and you are the adult.
When she wants to argue, tell her you love her. When she is disrespectful, tell her you love her and when she is cuddling you and playing with you, tell her you love her.