Lady Iceheart?

[Velaethia]

Is lady iceheart's appearance obtainable for players?

[Iscah]

Not exactly, no.

You can use her character data as a starting point for colour settings, though it says her face is a custom model so you'll probably have to play around to find what looks closest.

Also her hair definitely isn't available, but have a look at the "Samsonian Locks" style from the marketboard/PotD and "Great Lengths" from the Gold Saucer, which would be the closest options available.

Her outfit is definitely obtainable: boots and gloves from Hall of the Novice, and there are a few versions of her robe design but the closest is probably the Direwolf Robe of Casting from the Wolves' Den. You can probably use the skirt that goes with it, too - from memory she actually uses the DPS skirt so you can't copy it, but it's fairly minor in the overall look of the outfit.

[Amnmaat]

Yes, you'd have to go Duskwight (clan) and use a similar long hair which they added in Shadowbringers, I forget the name of it though; I think it's a craftable/buyable hair at the marketboard.
But if having the exact same hair then no; the excuse the devs would give is that "it would clip with everything on normal players."

[Iscah]

But if having the exact same hair then no; the excuse the devs would give is that "it would clip with everything on normal players."

It could be that, it could be that too many people using that style at once would put too much strain on calculating movement. In that case it's fine when it will only ever be that one NPC.

For a similar thing with items, the wedding veil is wearable everywhere but it's replaced with a longer, floatier version for the bride during the wedding ceremony. It can handle one character (maybe two) with that model, but it's not going to let an entire crowd of people use it at once.

[Jennika]

Meoni gave it a go, didn't turn out bad.

https://youtu.be/mGoifaYN7hI