QuickTime 10.4 Screen Recording only records video, not audio.

My girlfriend was interviewed on a local network news program and I 
would very much like to make a video of the story while its video is 
still up.

I tried QuickTime "Screen Recording" and was very disappointed that 
there was no sound.

i suppose it makes sense that "Screen Recording" only records literally 
the screen ... but it's still disappointing.

Audio Recording only records audio input through the microphone.

Is there any way to get an audio input from the online video?

I'm sure many people will recommend geting specialized grabber software. 
  Unfortunately, I don't think there will be time for that before the 
video is removed from the station's website.

OS X 10.13 High Sierra, QuickTime 10.4

-- 
Dudley Brooks, Artistic Director
Run For Your Life! ... it's a dance company!
San Francisco