Hello,

1. As she's still married, she cannot compel you to marry her as it is illegal.
2. However, she can file criminal cases against you including having physical relationship on promise of marriage and this can land you in serious trouble.
3. You will need to file for an anticipatory bail on to the premise that your relationship was mutual on consent and there was no promise of marriage on your part and that you are being blackmailed now.

You cannot be forced to marry against your wishes 

2) record her abuses 

3) file police complaint against her 

4) I presume you did not have any physical relationship 

You cannot be forced to marry her against your wishes 

1. If you have had physical relationship with her with the promise to marry her, no charge of rape can be brought against you now since you can jot marry her now as she has not yet been divorced.

2. Disconnect all relationship with her now.

1. She is not yet divorced for which you can not marry her now.

2. Disconnect all relationships with her.

3. She can not claim that you shall have to marry her for the sole reason that you have had consensual s*x with her few years ago when she was married and had promised to marry her after she is divorced.

Hello,

1. If you choose to continue in the relationship and eventually marry her inform her in no uncertain terms that you need to be an equal partner in the relationship and she cannot be imposing and aggressive.
2. Send her a message either in mail or on whatsapp about what you think and what your expectations are in the relationship so that there's some record of what is happening in case you need to defend yourself in future where the entire blame will shift to you. 

dear you are free to leave her. of course she can file cases against you as indian law is free for all to misuse but you have to meet some good lawyer to discuss your case and you can certainly save yourself. If planned well then you will come out of this relationship unscathed. till you meet a good lawyer, I will suggest you to be sweet to her and record everything like sms and audio video so that you may show these if required. good luck

regards

If she is still married and not divorced yet, you can inform her that you cannot marry her due to her marital status.

You can inform her that you are perturbed by her continuous nagging and tortures including mental harassment, foul mouth abuses.

You can issue a legal notice to her instructing her to refrain herself from interfering in your life anymore and also from contacting you either in person or through any media/manner especially because of her above mentioned behavioral attitude. 

You can warn her that you will file a defamation case agaisnt her if she is trying to defame you on the basis of her false claims on you besides lodging a criminal complaint against her for her acts of harassment and criminal intimidation.

You can discuss with an advocate in the local and proceed as suggested.

If she is not divorced and her marriage is subsisting then she cannot demand you to marry her.

It is will be illegal and invalid if you marry her during the subsistence of her marriage and the spouse living.

You can inform her about this legal fact and abandon her company and the relationship with her, also you can  arrange to get married to another person before she gets divorced from her husband.

If you do not want marry her now don't marry. 

Who said once you made any  promise you must marry under any circumstances. 

There is nothing such compulsion in law. 

Intimate her by writing your intention of not to Marry her. Briefly describe the reasons behind such decision.

Marriage is a religious alliance. Not a commercial contract. Here promise has some different footing.  

Do not go by any high court or Supreme Court judgement without knowing the facts and circumstances of the case. 

Remember a blackmailer hardly stop blackmailing until things reached to dreadful end. 

So be ready to accept sharing your story by that lady as law does not provide any bar to such sharing. 

Law also not compel you to marry someone whom you do not like even if a promise is made. 

There are lot of supreme court judgement where it is held that such promise losses it value in changed circumstances. 

So my advice is not to worry in such situations. Inform your intention alongwith reasons. This will keep you safe. 

Engage lawyer if any case or police complaint is filed. 

- Supreme court declared that , when  a man and a woman in love live together , is part of the right to life and not a criminal offence, and further live-in relationships is legal in India.

- Since, the said woman is black mailing you in the garb of relationship, hence her such act is against the law.

- You can lodge a complaint/information with police for your safety against her for extortion under section 384 of IPC, and for threatening to implicate in false cases.