While she did strike me as profoundly unhinged (hell, anyone would be after a century in solitary confinement), I'm not convinced this isn't once again Larian being unsure about what is Deva, and what is Aasimar. It doesn't help that celestial and devil genetics aren't exactly completely straightforward in all cases, nor without exceptions. We don't even know if the de facto 100 year prison sentence didn't weaken her considerably. This is the same game where 3 mortals somehow enslave a netherbrain. Additionally, because of gameplay limitations, dozens of characters are "leveled down". Her in game strength cannot be expected to reflect her strength in lore. Larian wrote themselves into a corner here. Make her reasonably strong, and she one turns the boss solo. Can't do that.
https://www.dandwiki.com/wiki/Demigod_(5e_Race)
Strictly speaking, the demigod race would be the best match for a real "daughter of Selune". They also do not age, provided they are supported by their parent. However, they're very clearly described as greatly varied, and aren't even necessarily that OP.
