So I have a 1 year old son. My sister came to help me out while I was pregnant(complete bedrest entire pregnancy) so she is here my fiance is working all the time. And I would waddle out and ask him how is day was on my way to the bathroom. Well soon she starts changing from her normal jeans and a t-shirt into skimpy a** clothes just before he got home. And would literally wait by the door for him like he was her man and would shout hows your day and all that crap as soon as he got into the door.(he's a man didn't pick it up yet) and she completely talked over me and got in my way to my man. (Mind you im not a jealous woman. My man tells bi*ches to back off and he is happy and I trust him 100%. But d*mn this girl.) So anyway, this keeps going on for 2 months and she is slowly trying to take my place stress me out so I lose the baby and thinks she will get him of something happens to me(legit heard her say this under her breath) and well my man and I decided to test a theory. He showed up early at the house before she could change and she ran to her room changed after he got home and starts strutting around the house. Im already mad because of hormones n he goes wow I guess you're right. So he tells her back off she is gross and wants nothing to do with her. So fast forward a year she is in a relationship and is moving out of our house now. Things aren't going well with her man and she is back at it but worse!!!! She is now wearing see through clothes and looks and me and gives me an evil grin and says I know that's the point. And when my man walks through the door she bends over and literally shakes her a** at him! And I ask her to grab something for me and she sees him coming she gets on her hands and knees and throws her ass in the air and shakes it. And she is calling me fat and ugly all freaking week!! Ladies what the f*cking f*ck is wrong with her?! Is she that narcissistic!? Or am I literally seeing sh*t?! I am at a loss for what to do.