Sounds judicious. You probably wouldn't get sued, and would prevail if sued. However, the question of how much human voice space Scarlett can lay claim to remains unsettled. Your example suggests that it might be quite a bit, if law and precedent causes people to take the CYA route.

Consider the hypothetical: EvilAI, Inc. would secretly like to piggyback on the success of Her. They hire Nancy Schmo for their training samples. Nancy just happens to sound mostly like Scarlett.

No previous negotiations, no evidence of intentions. Just a "coincidental" voice doppelganger.

Does Scarlett own her own voice more than Nancy owns hers?

Put another way: if you happen to look like Elvis, you're not impersonating him unless you also wear a wig and jumpsuit. And the human look-space is arguably much bigger than the voice-space.