> When studios approach an actress A and she refuses, then another actress B takes the role, is that infringing on A's rights? Or should they just scrap the movie?

The scenario would have been that they approach none.

Your scenario leads to the disenfranchisement of lesser-known voice talent, since they cannot take on work that Top Talent has rejected if they happen to resemble(nobody here has seen their doppelganger before? How unique is a person? 1 in 5 million? Then there are 36 million of that type in just the United States alone). Perhaps it's time to re-evaluate some of the rules in society. It's a healthy thing to do periodically.