My mother-in-law recently saved a Betta from being flushed by friends who thought she was too sick. I don't have a before picture but she was emaciated, her fins were mostly gone and she was entirely grey. She has already perked up a great deal, her fins are growing out and she has developed a beautiful purple-and-pink color (looks blue in the picture, but it's really a deep purple).
My mother-in-law has kept a number of kinds of fish, but never a betta. She has been keeping her in admittedly a too-small vase and she is probably a little chilly, but she has already come so far in a few weeks. We are getting her a good setup with plenty of room and a heater and I'm helping her nurse her back to health long-distance. I just wanted to share how much better she's already doing. (Forgive the crappy cell phone pictures.)