But this is not a huge factor in the real world when it comes to the meat industry. Cat food is not nearly its main driver.

So it’s just a matter of degree? Meat could be a delicacy for humans as long as we weren’t overconsuming?

I think it would be ethical on the part of the aliens to strive towards a solution for their diet that doesn’t involve killing or harming sentient beings

If they’re obligate carnivores, what could they kill instead? Killing any living creature for food is morally equivalent.