Who is the older of two, Goldberry or Tom Bombadil? Tom found her long ago,but she was there for him to find, couldn't she be older than him?
In the Fellowship of the Ring Tom describes himself as:
Eldest, that’s what I am. Mark my words, my friends: Tom was here before the river and the trees; Tom remembers the first raindrop and the first acorn. He made paths before the Big People, and saw the little People arriving. He was here before the Kings and the graves and the Barrow-wights. When the Elves passed westward, Tom was here already, before the seas were bent. He knew the dark under the stars when it was fearless – before the Dark Lord came from Outside.’
This implies he believes himself to be older than Goldberry.
Goldberry is the "River-woman's daughter", which means that she obviously has a mother. Tolkien never states exactly who the River-woman is, but if Tom is Eldest, then Goldberry's mother must be younger, so Goldberry is therefore also younger.
Ah Bombadil. Unfortunately I do not have the precise reference to hand, but I recall reading an essay by Tolkien (was it Tree and Leaf?) at some point where he said that Bombadil is poorly explained in LotR, because he is part of the mystery aspect. He is poorly explained because there is much about the world around us that is poorly explained. This is also part of why the One Ring has no effect on him: Bombadil is outside of its domain entirely.
Goldberry is daughter of the River woman and "Tom was here before the rivers". I think that settles it.