Why does Pallas transform or disguise herself?

In one version of the myth, Pallas was the daughter of the sea-god Triton. She and Athena were childhood friends, but Athena accidentally killed her during a mock batlle at a athletics festival.

Absorbed over what she had done, Athena took the name "Pallas" for herself as a sign of her grief. For this, Pallas transformed herself in another entity, known as "Pallas Athena".