Given a choice between the two, the non-reacting dog seems pretty nonchalant to me. (If it were entirely my description to write, I'd have said "resigned"; but if we're sticking to the two commonly confused adjectives... while the dog is probably confused as to why it's suddenly under kittenish assault, visually it does not react, so as a non-omniscient narrator I'd choose 'nonchalant'. What was your reasoning for making the reverse call, if I may ask?)
Re: All I see is "laying" ;__;
the dog is closer to nonplussed than to nonchalant
Nonplussed: perplexed, confused, taken aback, discomfited.
Nonchalant: imperturbable, disinterested, placid, unflappable.
Given a choice between the two, the non-reacting dog seems pretty nonchalant to me. (If it were entirely my description to write, I'd have said "resigned"; but if we're sticking to the two commonly confused adjectives... while the dog is probably confused as to why it's suddenly under kittenish assault, visually it does not react, so as a non-omniscient narrator I'd choose 'nonchalant'. What was your reasoning for making the reverse call, if I may ask?)