Suicide threat from ex girlfriend unable to understand what to do

I had a girlfriend with whom I had love relation for 8 years However, we used to have lot of fights in between due to which we decided to step back and move on without each other. After few days when I thought of someone to move ahead, this old girlfriend started giving threats of suicide sometimes and sometimes she used to say go with that girl if you feel its good. Now she recently did something at home due to which her cousin started threatening me saying If something happens to her, she will take revenge from me. I really don't understand whats going on now. What my ex is doing and what she has done that her cousin started threatening me very badly on social media. Can you please advise what action I need to take as we broke up mutually first but this girl had some problem with her thinking and now putting me in trouble.