You just need to do a formal divorce. This is what you should do if you want to marry again in the future. From your point of view, you have to do it anyway. This will save your effort to report to police that she is illegal worker here. After formal divorce, she is automatically illegal. You will have no responsibility for her.
If you really want to help her, divorce her after she find a new hou*****and. Otherwise, just do it now.