You can also write "forwarding address requested" on the envelope and if she did have mail forwarded you will get a post card from the post office with the information on it.Check the court files and see if she filed notice of her move... send a letter to her last known address. When it comes back check to see if it is "unable to forward" or "forwarding expired"... that will give an attorney or a PI helpful information that would keep your costs down.