Dear Mr. Sanjeev,
Any legal action you may initiate may provoke her and in retaliation she may immediately approach police with false cases for the offences of dowry demand and harassment or cruelty by husband and his relatives namely mother, father, brothers sisters etc., including the pet dog which might have barked at her as a recognition in affection, when she entered the house. For this the only precaution is as and when you are summoned by police even for minor inquiry, the first thing to do is to take anticipatory bail and then attend the investigation session.
The case in the court subsequently can be challenged during trial accordingly on the basis of merits in your side.
If your brother is no more interested in continuing his married life with her, he may very well file a divorce case against her on the grounds of desertion and mental agony.