I did this for a friend several years ago. She had a comforter that had lost it's puff. She wanted me to add more to it. First, had to unstitch everything, then add batting and resew it. It was a king size. I said I would NEVER do that again! More work than making a king sized quilt from scratch!
You are a great friend for doing this - glad you were rewarded with the digital camera. :)