This is very far from the worst problem in the world. But I do think it's ridiculous that many Hollywood studios have adopted rules against depicting characters smoking, but have no problem portraying vastly worse behavior: rape, murder, torture, slavery, all kinds of bigotry, and so forth.
I know the fear is that kids might see the movie, decide smoking is "cool," and then take it up. But you can make the same argument about virtually all the other things listed above.
What if kids think Darth Vader is cool, and decide it's therefore OK to massacre children (as he does in Revenge of the Sith) or destroy entire planets (in the original Star Wars movie)?
What if they decide a serial killer portrayed in a horror movie is cool? Even if Cruella isn't allowed to smoke, she still presumably brutalizes puppies. What if kids decide to imitate THAT?
In addition, if your kids really view Cruella de Vil as a role model (a character whose very name marks her as a villain), you probably have much worse things to worry about than smoking.