They used already recorded voice overs from previous episodes to do her role in this last episode. They didn’t want to overdo it and make it obvious, which is why she has so few lines. Same with Ron’s line.
I'm a little excited for the new season. But with the passing of Jessica Walter I would have been satisfied how they wrapped up Season 12. A very fitting ending for Jessica Walter's and Ron Leibman's characters. I think it was done exceptionally well.