Marriage & separation

My younger brother had married on Dec'14 since his marriage he was fall in sick which was gradually increased & doctors advised him to take DOTS medicines but unfortunately he died on 22 may'15. In between his wife goes to her maternal house with consent of my brother to attend a family marriage ceremony there that time she taken all her gold jewellery to celebrate that marriage on April19,2015, since then she was not coming back to his in-laws house and his guardian & relatives are coming to our house and asked to returned the all gift which was given in connection with there marriage, she also agreed that she was taken all gold properties and she was not interested to live with her husband. as soon as his death we also inform her but no one of their family was come. Again we call them to collect their furniture but no answer, Now She threat us over unknown telephone to give us under police custody as we hide the disease of my brother before her marriage. Now my question is :- 1. We really don't know about any disease of my brother, then how can she demand this allegation? 2. What types of action she can be taken? 3. What should we do in such a situation? 4. Before marriage they are knowing each other since one n half year then every thing was right , now how can she told that he was a patient? Pl. advised/ help me