My friend caught me having sex with his sister! what should i do?

Ok so iv'e been BEST friends with Colby soandso for over 13 years and I have known his big sis Trudy soandso for that long to and I dont have a crush on her or anything shes quiet ugly, but she does on me. So all of sudden she starts threatening me to do her this past week and I kept telling her "no!" I smoke with my bud Colby so.. one day after getting high i woke up on her bed next to her.. I think i was drugged and he saw me there with her so is there any chance of mending my friendship with Colby?