I don't have a video about it, sorry, but you'll find some on YouTube, I imagine.
It's very simple, just circle the area (with a little bit of buffer around it) then drag the area onto another area of similar texture.
This looks like fairly standard file corruption. Just save them again from your master files, and send them to her again. I'd be surprised if it happened twice.
So if you wanted to do a black-and-white of this one, use Channel Mixer for your conversion. Add the Channel Mixer layer, check the "Monochrome" box, then enter 0%, +100%, 0%, 0% for the four sliders.