Voted Best Answer
Feb 10, 2021 - 02:01 AM
Using "elle" wouldn't be grammaticallyu wrong here (although a little strange in this context as you explained James), yet if you used "elle" then you'd need to add an E at the end of the adjective "important":
elle n'est pas très importante pour lui.
Yet in this case as we said, it's much more natural to use "c'est" since we're referring to the whole sentence rather than to the object itself. :-)