Husband died and now a woman wants share in property

Can a woman who had an affair with a married man who has two kids from his marriage demand for property share after his death?? His wife is not having a marriage certifiacte and she knows that so taking advantage of that she is asking for share in property claiming herself as his wife and says she has photos with her of same. His wife with two kids has a voting card and a passport mentioning her name with her husband's name and which shows they are married. This man was having this affair from past 13 years and was threatening his wife that he will leave her if she will tell about it to anyone in the fear of losing her husband and her kids losing a father and living a life without money and food and shelter this poor uneducated woman dint tell anyone about it and beared it for years. But now after his death this other woman wants share in property. This was having an affair with her and she knew he is married and has two kids from his wife. And due to some fight man and that woman decided to get break the relation and they made an affidavit i which it was mentioned that they are ending this affair relation and and shall not see eachother anymore and he shall give her 6 lakhs rupees he borrowed from her for some business work and they both had signed it. Wife is ready to give her 6 lakh rupees but she wants more than that and is asking her to give share in property. What can be done i this case. Its very urgent Please help