So I went to my cousin's house yesterday and stayed the night while my sister was here at my house watching my little sister and staying with my mom. I just got back home a few hours ago to find a horrible mess in my bathroom and I'm pretty mad about it. My sister is 20 years old, very immature and lazy, she wont even walk a block to get food for my grandmother and her self, so she is lazy. She apparently took a shower today and she left before I came home but when I did come home, I seen her clothes on my bathroom floor, her dirty towel, and her washcloth in the shower that she used. What I am really mad about is that she has an std down there and it is something that wont go away, it is herpes. She knows it could get spread it by leavng her underwear lay around. So I cleaned it up by putting her things in a bag and throwing the wash cloth away and cleaning my bathtub out.

Why is she so lazy? What should I do about this?
She doesn't live with us. She lives with my grandmother.