Disclaimer: Latest update, refined Illustrious version.
This LoRA used mostly pictures taken from Genshin Impact's animated short and only a few fan arts since I originally aimed to make a LoRA of her young appearance seen in the flashback short, however it can generate an adult version if prompted correctly, add "anime screencap" and/or "anime coloring" to prompt if you want renders to resemble the short anime look.
I also recommend using This Age Slider LoRA to better control her age appearance.
Special mention: Tyberzandari for Illustrious version testing and some preview renders.
Illustrious Weight: 1
Pony Weight: 0.8
Tags for both versions:
Trigger: gi clervie
Character: green eyes, long hair, ahoge, red hair,
Outfit: white dress, necklace, short sleeves, off shoulder, short dress, frilled dress, hairband, hair ribbon
Extra Info:
As mentioned, you can always experiment changing her age with basic prompts, but it is recommended to use an age slider LoRA, in the source material she used to wear a white layered dress with blue hem, that is a bit inconsistent for some reason but be my guess and experiment with "multicolored dress", it might help.