1. Have the husband and son been released on bail by the court? Since they were arrested it shows that police is taking the matter seriously.
2. The legal remedy available to victims is to move to court and file a case for recovery of money against her. If you suspect she has some properties in Chennai then move to court without any further delay and seek a stay against the sale of those properties by her. In the event you succeed in the court her properties may be sold and the sale proceeds appropriated towards the recovery of amount due to her victims. If she succeeds in selling the same you may not get anything.
3. The above being said, your mother and all other alleged victims will have to prove that they paid money to this woman. The stamp paper subject to its contents and the bounced cheque may be of some help.