My sister is being a pervert..?

Okay well my sis came to live with me in february and shes been a pervert i think shes a bi.. Sometimes i think its because of her dad, probably crazy. Okay and my niece is abnormal kind of because her dad was drugged and all. My sister is 14 my niece is 8 but acts like 5. So my niece came to visit like a week ago amd yesterday my sister was acting like a perv. She got up like so close to her and stuff and keep on hugging her real close and kissed if that means anything but my sis is a perv soo. At night they were playin around my niece was Tryna look into and probably touch my sis breast, even though my sis kinda stop her she probably liked it. Then my sis did it back even tried to go down there. Today my sister just a few minutes ago was watchin a show with her but like she immediately Had to carry her and pick her up n bring her so close in the bed, they look like gf and bf layin together. And my sister tries to carry her and all my niece dont like it and she runs and my sis chases her and tries to bring her back to the room. I dont really like this its not right and i really dont want my niece to be like that.