(You could blame reading too much Silmarillion and other mythology-themed works for this. Also, associations with names and appearances, such as "Juniper > Jupiter > celestial > angel" and "Wallflower looks like a tree, so she might be a dryad")

Once upon a time, the world was a more dangerous place. A certain parasitical species of tree evolved to become more humanoid: while losing roots in favour of quick legs allowed them to run, it also made them more vulnerable to predators.

In one tribe of dryads, one young female was one of its bravest warriors, fending off predatory beasts and teaching her people how to cook. When the other tribe members thought that the gods had bestowed wisdom unto her, Wallflower stated that she learned from "a being of immense light."

With her and her friend's guidance, the tribe claimed some land for themselves, and gradually became into a basic chiefdom where its inhabitants now live in houses instead of huts, and who managed to master the skills of lighting fires and writing. The celestial (as the being addressed herself) felt that her job on Earth has been finished, so she made a crown to appoint Wallflower as her successor to lead the tribe, as Wallflower had learned enough skills.

Her tribe — later a kingdom of plant people — remembered her henceforth as "the one who studied under a walking star".