Yeah, no. We've got the original text and that calls it 長鯨 (so "trường kình") and if 8housesofelixir is to believed, it's a standard literary trope.But how do you know Ca kinh wasn't applied to orcas much later? Would she even be aware of them?
Likewise, kình is a Middle Chinese word, Middle Chinese would come into existence centuries after her death so she couldn't have called it Cá kình herself.
The word for whale in Vietnamese I could find that isn't Chinese in origin is cá voi (fish elephant) which is reconstructed as [a-kaːʔvɔːj] some 500 years after her time, which is where I'd end this small excursion into the languages concerned.