My brother's wife not returning home after sending 2 Legal notice.

Its been 4 and half month now she is not living with my brother.it's not known whether she is a really at her home in village or not. because my brother's wife and family is not at all cooperative.In August my brother sent the first legal notice to his wife to get back home. she haven't given any answer to 1st notice. nafter sending second notice she did not received that notice and sent back. Then we received her 1st legal reply during navratri. and she had put some false allegations against Me, my brother, and my mother. she has mentioned in notice that she is ready to come to home. But she is not coming. problem is that she wants divorce she don't want to live with my brother. but she don't want to file Divorce. she is waiting for my brother to file petition for divorce, so that she can demand for mentaince. how can we take Legal advantage of her assets until she don't come to discuss? what to do next?nshould we file petition or not? How can we get out of this problem ASAP?