Ironically, a similarity to a real, live person without an agenda is not a legal problem unless there’s an implied endorsement from the person. (Which I think was one of the goals here.)
But characters in movies and books are subject to copyright and are considered the intellectual property of the rights holders.

So like, if I wrote a book about Wolverine and used other Marvel X-men, Marvel could sue the shit out of me. Or if I used AI to create Hugh Jackman (as Wolverine) to endorse my bandaid product line, I could also be sued by both Jackman and Marvel.

I think it’s obvious here that Sky was intended to represent Sam from Her, and is almost certainly trained on her voice data (which is copywritten). After a few days thought however, I’m less certain of the argument this could be seen as a false endorsement scheme, since Johansson isn’t mentioned anywhere. (Despite the character being solely played by her, and the numerous attempts to have Johansson work on the project in an official capacity.)