YA adaption and a curse

please help because search engines no longer function at all and nothing is popping up. There was a segment in this YA adapted film about magic and adventure or something. Some lady ate a magic berry that was the most delicious food a person could eat, but it cursed her for eternity to only be able to consume only the berries. she wore a white dress and she was involved with pixies or a similar type of fantasy little creature