However, she recently became engaged to be remarried and has volunteered to stop receiving alimony. We are on amicable terms so I believe her.
My question is what paperwork do I need to complete and file with the court to make her decision to terminate alimony legal?
This answer only includes general divorce help for men since I am only licensed to practice in Oklahoma and am thus unable to provide financial advice on divorce based on the laws in your state.
Where I practice, courts are vested with the power to change the terms of an alimony award upon certain contingencies. The contingency that seems most fitting in your case is remarriage of the party receiving the alimony payments.
Since your ex will soon remarry her fiancée, you may have grounds to modify and terminate the alimony payments. Since your ex has volunteered to forego alimony and the two of you are on good terms, you may consider filing an Unopposed Motion to Modify Alimony under the same case number as your divorce so that the court will know that both parties agree the alimony payments are no longer wanted or needed.
Then, you would simply need to submit an Agreed Order Modifying Alimony wherein you officially and legally bring the payments to a stop. Depending on the law of your jurisdiction you may be able to present these documents to the judge together and finalize it the same day.
Please understand that my opinions are based upon the limited facts that you provided to me. For a more in depth discussion on alimony advice, I urge you to contact a divorce lawyer.