Is this a prolapse of the uterus or rectum? When you say prolonged farrowing, how long? Was she straining and getting nowhere or just took a long time to have 7 piglets? Farrowing can take hours.
If it is rectal and small it may pop back in or it may need putting back in. If it is the uterus it may continue to push out and you will need the vet as internal bleeding can happen.
Are you absolutely certain it is a prolapse and not just bruising and swelling.