Aetheryte

[Keever]

Y'shtola

Y'shtola's insistence that she is twenty-three is a joke previously used in the description of her ARR minion:

If we are to take her word for it, the Circle of Knowing Archon has seen but twenty-three summers.

There may or may not be anything to read into there. I tend to assume it's just another case of devs/writers joking around in the absence of stronger evidence. Just like "Sharlayan cosmetics".