What I find interesting here is the echo of "Amadeus"--with Carly as Salieri. But rather than trying to kill the rival (or her reputation) this Salieri just writes a cutting song about the king.   

Certainly not practical for Salieri--and after all Salieri did have quite a good career, though he seems to have realized--if anything in the play can be believed--that Mozart was the genius he'd never be.

And the subject of the song in question was in fact Geffen--and the reason was that Carly did in fact resent the attention lavished on Joni Mitchell--all it proves is that Geffen recognized genius when he saw it.

Consider the difference in the bodies of work of the two women. Who will be immortal? Not Carly--except for this one song.