Legal Openion Required On Family/Marriage/Relation Matter

I m 35 yrs married male and having 2 new born daughters. When i was at the age of 32, i had proposed a 18 yrs girl (belongs to same community and area) and she also accepted the proposal and we started talking on phone and message. But since i was at 32 age hence i clearly told her that i had to marry in next 6-1 yr max as my family was already searching Bride for me. But she was just 18 and passed her schooling, i decided after many thoughts that we should avoid this relation and we agreed and i moved on and got married. We had never met a single time till the date. Now after 3 yrs again i contacted normally via whatsapp and our talks r started. Since this time my wife was pregnant so she was not with me hence i was able to talk thru phone call, video call. But every time i clearly informed her that i cant talk forever like this coz now i hv many responsibilities and in coming month i will be a father. But she had taken all this very lightly and said that ok talk till possible. After 1 month of contact she planned for meet me face to face 1st time, initially she and i many times denied bcoz it was not a good decision but then some how i convinced and we met. We met and we stayed together for few days and also had sex mutually. Some times she talk like very mature person and was saying that yes you hv ur family so i have do all things as per family so with this type of talks, i believed ghat she is matured enough. But now she is in love with me badly, crying on daily basis and insisting me to give divorce to my wife and marry with her. Now she is threatning that at any cost i have to marry her by hook or crook. She also called my wife and told her that ur husband slept with me so now u leave him and give divorce. She knows very well that i never gave any commitment to her about marriage and love. Every time i clearly told that i am already married so i can not marry her and this was my stand from day 1. Initially she was ok that ok dont marry but atleast meet once but now after meeting she is pressuring me to meet again and again, she is forcing me to talk to call, which i denied now. Now kindly help me to know my legal rights and how to escape from this. As now it is impacting on my family and her too. One this i left, in past she was a patient of depression and she has symptoms of Bipolor Desease (mood swings).