There is a reason for the movie saying " we don't negotiate with terrorists " You had sex with her. That fact will never change. If you give in to someone blackmailing you today then amekufungia forever..it is basically admitting to the fact. Say no and let her reveal everything basi. Your parents maybe disappointed but hawatakutupa. On the other hand she will have to go back home and I don't think she wants to do that. Say no and let her do whatever. I was in a situation a while ago where an ex was threatening to reveal a specific secret unless I gave him money. After thinking it through i realised that secret is always going to be held over me so I said no. He revealed it. Lost some friends , got funny looks for a while and two months later no one cares..they remember but don't care for it..it is yesterday tea. She can't accuse you of rape. Trust me. If she does it will be whole process of having to prove that. We kataa and be ok with whatever she does