My little sister came home form school today saying her best friend v*'d twice at school today. She had lunch with the girl and sat two seats away from her, and also was late for class because she was sitting with her while she waited for her to be picked up. My sister knows about how I feel, but she's not necessarily the most hygienic. She said she washed her hands before and after lunch but I don't necessarily believe her. She pretty much just screwed over the whole family, and she was hanging out with the girl for the past two days as well, so there no way she wasn't infected.
I'm just siting her silenty panicking because my parents aren't home and I'm supposed to be getting better but now she's brought this in the house and I already yelled at her for doing that and I feel like a shitty big sister but she just screwed everyone over.
What do I do ?