.... uhh where does that SH thinks Karlach's unintelligent? From what conclusion did you arrive at that?
I actually misremembered the quote, it's a bit farfetched to assume that's what she meant. For context, it's: Shadowheart: We may need to increase our camp provisions now that we have Karlach along for the journey - those muscles don't run on fresh air, I'll wager. Still, she'll be useful in a fight.
More of a justification of bringing her along than anything else.
Still doesn't imply anything to do with her being Unintelligent. Just that another person has been added... nothing to do with intelligence... could be something else I'm not seeing but not that.