A Professional Wedding Officiant may perform a Civil Ceremony which is also a Legal Proceeding in which certain things need to be said. Does your Friend know what they are?
Did you know that there is no Wedding Ceremony in the Bible. A Minister brings their Bible to a ceremony to read various biblical verses and passages into the ceremony making it a religious ceremony.
With that being said, there is also the proper handling of the Marriage License to consider. Does your Friend know the proper procedure?
Will this be your Friend's first ceremony? It may come across as such whereas a Professional Wedding Officiant has been trained and will have had valuable experience to ensure your Wedding Ceremony goes off without a hitch.
Can your Friend perform a Rehearsal and have a full and clear understanding of how to conduct the Processional and Recessional, the proper seating of parents and other family members?
Will your Friend have a Backup in case of an emergency? These are things to consider when you ask a friend to sign online to become an Instant Minister.
Writing poetry and adding vows does not make for a ceremony. Your Friend should know the key elements of a ceremony. Where will they learn this ? This is just food for thought.