Ending of relationship

I m married women.I married in 2014.Me n my hubby r happy in our life. we have 8 months old baby. My husband is loyal with me,before marriage he told me about his affair. He promised me that after marriage he will end his relationship but it took time.He was in relationship with a married women. She was not staying with her husband. she has not taken taken divorce .After marriage they were in contact they were meeting they were talking to each other.He started making distance with her. Now she was demanding to stay with my husband at my home like as a wife.She is demanding money every month.My husband use to give money every month.She is telling him that u r busy in your family not giving time to me.she is threatening to my hubby that if you will end relationship and will not give money then i will harm to your wife n baby sometime she is telling i will kill you n kill myself. Today she met with my husband and was again demanding all thing. He refused then she told that she already spoke to lawyer he told that you have right to demand all thing.When my husband refused then she took rat killer poison and was ready to eat. please guide us what to do. we are very upset.