What can replace no overnight guest so you can have your girlfriend move in with you?

A provision that says you can have overnight guests. Or you could marry your girlfriend and she would no longer be a guest.

If your Judgment of Divorce contains a provision that prevents either Party from having an unrelated member of the opposite sex spend the night, and you now want to change that, you will have to file a Motion in the Court where the Judgment of Divorce was granted, requesting a modification of that provision of the Judgment. Whether you succeed is dependent on a variety of factors, but if your relationship with your girlfriend has been long-term (i.e., over a year) and exclusive, that will likely help you.