New Gods stop aging at thirty, and Artemis was a teenager at the start of this arc, so if they've been away for years of personal time she's going to look like an adult.
Pretty sure New Gods stop ageing at whatever they think their prime is, and Grayven keeps saying 30 because he's used to being a 30 year old man.
If Artemis still thinks of herself as a teenager, she might still look like one.
If she'd stayed on earth and watched her (non-godly) friends age, she'd probably have aged with them.
Plus, I mean... youth is often an aspect of maiden goddesses like Artemis.
Heh.
No, seriously though, she probably looks like whatever she expects to look like, and since she didn't watch her friends and family all grow older...
Though, how long to sheeda live? Do they visibly age?
It'd be interesting if Grayven said something like "I don't know how many years it was, but I went through four high priests. Sure, one of them got shot and I had to execute another, but the last two lived long enough to grow old and die, so..."
I kinda want to know how Artemis spoke to her Sheeda minions. We know how Grayven do, but the way she wouldn't meet anyone's eyes before she left was a little...
Did they worship her? Did she execute people for treason? Did she have friends amongst them? How did she end up as the head of their alliance?
What did she go through when Grayven wasn't around?
... how did he get from 'centuries of offscreen conquest and civilisation building' to 'thirteen years'?! Does that mean that Artemis is a very young looking thirty-year-old? If Grayven isn't nearing his thousandth birthday any more does that mean that Luna is cradle-robbing once more?
Her starting age when dumped into Sheeda-world + the first 13 years spent in sheeda-world = 30, the point at which she'd stop ageing.
So she would have 13 years of being changed by this world, but Grayven would have zero, because he was already 30 to start with.
Is how I read it, anyway.
Maybe there was another 500 or 5000 years after that, but that time wouldn't matter because they'd be thirty, and their experiences won't shape them nearly as much.
The point Grayven was making, I believe, was that Artemis should have spent nearly as long in sheeda-land as she did in her own time, (before new god ageing stopped and locked her into her present state forever) so her personal identity should be as much 'Conquering queen of the sheeda' as it is is 'Gothamite vigilante'
But.. for some reason she still wants to go home, and doesn't seem to have built a family or a network of friends here, even though she's been here for so long.