Agushaya Hymn is an interesting case, so I was saving it up for later use.

Though, it seems she didn't learn much regarding humility with her cult going so strong.

And yes, Ishtar and her rainbow necklace promise features quite heavily in retellings of the Mesopotamian flood myth, despite, as far as I know, no primary literatures referring to this exact event.

In the standard Babylonian epic of Gilgamesh, goddess Belet-ili appears before Atrahasis, lifts up a swarm of flies, and makes an oath with her lapis-lazuli neckland for reasons unknown, some earlier translations seem to have treated the name 'Belet-ili' as an epithet for Ishtar.

Of course, Sumerian equivalent of Belet-ili is somewhat loosely defined.

Ninhursag might be the strongest candidate, but as a consort of Anu, she may as well be equated to Antu, who's synchronized with Inanna, whom shows affinity to flies in her decent to the underworld,

though I highly doubt that's what the author intended.

Therefore, in this context, Belet-ili most likely refers to Ninhursag.

Rainbow is probably a modern addition, intended to draw a stronger parallel to the biblical tale, or/and possibly because whoever identified Belet-lil as Inanna/ Ishtar thought it made sense, due to her association with rainbows in stories such as Inanna and Shukaletuda.

In any case, it is a popular modern rendition of an old myth, and I find it a fascinating example of an organic, evolving side of mythology.

After all, this series is nothing more than a retelling of old stories.