I [25F] just found out that my sister [19F] has been having sex with her boyfriend [20M] in our house while our parents are away.

To me that's just disrespectful to do something like that. I told her off and she has been making snide comments back at me for something that isn't my fault. Like for example she said, "I'm older I should know better, I'm being immature" and then she goes on to say that I'm 25 and acting like I'm 5. I don't like how she's has been making these snide comments towards me. What should I do?<br><br>Edit: To everyone this is not a throwaway. I didn't think it was a big deal, but it is. I just let it slip to both of my parents and they were both super pissed off, so I told them everything and my parents were super pissed off. They told my sister to pack her bags and that she's moving out and in with our grandparents. My sister is angry and she said that I'm a "snitch" and a "bitch" as her parting words as she left.