Stalk

There is a girl who is having affaire with my friends and they both with mutual consent court married each other without thier family consent. Now they both are having rough time and my friend dont want to be with him so he does not lives with her same is from the girl side, she also dont want to be with him but they both meet each other frequently, drink together , roam together. I dont contact my friend by the time they are having fights n all but whenver my friend dont meet him or disappear she start calling and messaging me and start questioning, where is he , did he called u up, did u meet him etc etc. They went to police station 3 4 times when girl complaint against against my friend. She falsly accuse me n other friend also that we help him n all that girl is in regular contact with my friend ,they both meet frequently and party together and when guy does not contact him she start calling n msging me n other friend. We dont contact our friend now neither we are helping him. I want to know how i stop that girl to bothering me as i am not able to focus in my office work n other work, she feels like threat evrytime she contact. They both married each other with their consent now having rough time so creating problem for others by calling, msging n by threatening. Please advice how can i stop that girl to annoy me. i have her all the msgs which she sent me n created mental torture to me