It really depends on the position of the prosecutor. If your wife has never been arrested or convicted before it is likely she will be treated better in negotiating a resolution than someone who has a conviction history of violent offenses. If there is a history of calls to the police involving the mother in law as an aggressor that can also go in your wife's favor to back up her statements that the mother in law behaved out of bounds. Provocation is not usually a winning defense, but a great attorney can certainly help put the situation in the best light possible and potentially get the charges reduced, dealt with through a diversion or pre-trial intervention program, or possibly dismissed depending on the evidence. By and large, prosecutors don't like cases involving ex-family members where kids are involved because they tend to have a greater amount of both contention and the potential for someone to lie about what happened if there is a goal of getting custody shifted, etc. Please seek the help of a qualified attorney in this matter. It is probably best to find someone who deals with both criminal law and family matters.