If they accidentally hired someone who sounds identical, that's not illegal. But if they intended to, even if it is a pretty poor imitation, it would be illegal because the intent to do it was there.
A court of law would be looking for things like emails about what sort of actress they were looking for, how they described that requirement, how they evaluated the candidate and selected her, and of course, how the CEO announced it alongside a movie title Scarlett starred in.
In the case of acquiring a likeness, if it's done legally you acquire someone else's likeness that happens to be shared with your target.
The likeness is shared and non-unique.
If you objective is to take someone's life, there is no other pathway to the objective but their life. With likeness that isn't the case.
Hiring someone with a voice you want isn't illegal; hiring someone with a voice you want because it is similar to a voice that someone expressly denied you permission to use is illegal.
Actually, it's so foundational to the common law legal system that there's a specialized Latin term to represent the concept: mens rea (literally 'guilty mind').