Question: IMDB lists a character named Sunshine, played by an uncredited Prudence Wright Holmes. Who is she?
Question: At the very end, Arthur's body is being carried away on a barge, with three women standing above him. Are those three women the fates?
Answer: They were the Goddesses of Avalon. A group of women who each have a specific magical power. They were the makers of Excalibur, healed King Arthur's wounds from his first battle and took him to his final resting place, readying him for the day he would be needed again.
Most Arthurian myths attribute elves as making "Excalibur", and also "Clarent," King Arthur's other magical sword.
Answer: Or possibly they were attendants of Arthur, who would set the ship on fire, then have the option to die with their king, or to try to swim to shore. The Vikings did stuff like that. Why not imagine that the Brits did too?
Answer: Sunshine is the name of one of Gueniviere's handmaidens. She is also mentioned in L'morte d'Arthur.