If your brothers wife has filed domestic violence case against your brother than the petition would show who are the respondents in it. Have you not checked the sme . Such things are common nowdays of filing false domestic violence cases to seek money in the form of maintenance and compensation . Check out the same and you dont have to bother . She has to prove the same with evidence .
she cant Add you at a later stage in the proceedings . Tell her to buzz off and the next time she tries to threaten you tell her straight forward go to hell and do what so ever you want . Now instead of you panicking you should make her panic since once she visits the court for each and every hearing you will notice her patience running out espically when its a false case .Visit a court one day and you will observe how you have to wait from morning to evening . and in a Dv case what order can they pass just a protection order thats all . There is no conviction . Only when the protection order is broken than criminal proceedings start .