So, finally caught up, and I mostly want to talk about really old stuff, so posting here.. In the episodes around Goldberry's cleaning day, there was no real consensus what exactly she was cleaning. I agree with the episode conclusions that she's spirit of water lilies (and possibly other aquatic plants) in the streams and pools of the river. My take on the cleaning day: At fall, plants would drop petals and leaves which would litter the slow waterways and still pools. A good rain would wash this out, downstream. So she's pretty much cleaning her room after making a mess in the River-woman's house.