She called saying she went to take off at a green light and heard a loud pop, and the car stopped moving with a random knocking noise.
Now, I’ve seen half shafts fail/come apart at the CV-joints. But I’ve never seen the shaft itself snap.
But then, if you look closely, the shaft tapers down from about 1 3/8" to less than 3/4" at the harmonic damper.
As the song goes, "You Ain’t Seen Nothin’ Yet!