She does have less pronounced even features than her BG I+II portraits. Though as a half-elf it isn't really a problem, though it does show that Larian's art direction is divergent from BG II in terms of fidelity to legacy characters. Really, what bothers me is that they really whitened her skin, particularly if they are going off of her BG II portrait (which seems to be what they are using for BG II) Jaheria was really not white in BG I-II so it's rather...jarring to say the least. She and her husband were from Thethyr/Calimshan IIRC, which is sorta the equivalent of Iberia & Morocco in Toril.
You've just sent me back looking at those old portraits and comparing them properly with the new BG3 model. I do think her BG1 portrait was as (or perhaps more) human looking than the new version, but I agree that the BG2 portrait from which her BG3 hairstyle is of course taken had bigger, more slanted eyes that I think of as more characteristic of elves. In terms of the human-ness/elfiness of her new model I think it strikes a reasonable balance.
But now you say it, and now I actually look at the old portraits, you're of course completely correct that she is paler and more northern European-looking than fits well with the possibly Mediterranean look of her old BG portraits and probably, as you say, her origins in Tethyr though I don't know much about FR lore on that point.
"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"