Blackmailing for having sex otherwise she will lodge rape case

One girl came to me stating that I have a period problem and her doctor told her to have sex but many a time I denied to sleep with her being a friend I did but on the context that It is merely because of you I don't want it. She accept that but after 3 weeks she repeatedly told me to have sex stating that otherwise she would lodge a complaint of rape against me while doing sex with me she was also in relation with other person and wanted to marry her, each others family know about their relations but just because he is not good in bed she come to me every time and got perganent with me so the guy left him and soon I get know that she had a misscariage while this drama is going i m busy with my enagagemnt and she know about it then a i got married now it's 8 month I m maaried but all blackmailing starts again she is telling me to have sex with her otherwise she would file a rape case and told police that I killed her child. What should I do help me please...... my wife know everything about this