Mail goes to my mother in laws house as we are between housing. She has withheld correspondence from court causing me to miss court appearance. Legal?

We are in between housing and having mail sent to my mother in laws house. She has stolen bank statements to use as detriment to my wife in probate case. Used These as evidence to support her claims. Also, she has withheld correspondence from the court causing myself to get a failure to appear warrant. She is knowingly doing this. What am I able to do?