I have heard this sentiment before, and unfortunately I am not convinced that the obnoxiousness of this character was intentional rather than accidental. I don't have much to back this up: basically my hypothesis is that Sanderson is trying to pander to a specific audience, to whom the witty banter he is attempting is appealing, and genuinely attempting to make Shallan 'cool' fits with this hypothesis. Furthermore, as others have also mentioned here, his other attempts at similarly witty characters have also been flawed, so there's that.

Did you get through the second book yet? I pretty much hated the first half of book one when shallan showed up due to way she spoke and acted, but the second book goes into much more detail about her baggage. Other characters also have in universe reactions to shallan that are smiliar to yours

I did read the second one, in fact one of the most jarring passages I found (see sibling comment above) is from this book, so I don't think learning about her backstory solved this issue for me.. But I see you and several others have made this same point so maybe I'm being curmudgeonly.

I think that Shallan, as presented, is written lazily and with a way of thinking and talking that has been forcibly transplanted from our (as in, the World, 2018) current culture and into a fantasy universe, which is jarring to me.