Shared nude pictures now girl is forcing to marry

I exchanged some nude pictures on whatsapp and the girl now is forcing me to marry her or else she is threatening me to ruin my life career and my family members life or commit suicide and write my name on suicide letter. Her mother calls me up every other day and threatens me and also asks for written declaration of marrying her or taking her suicide responsibility. But the exchange of pictures was mutual without any promise of marraige or love or whatsoever. Please advise me what to do?