It's even easier to walk someone through with a command line. I've done it, reciting the magic incantations for the Windows recovery command line to a relative who didn't even know the difference between Windows and Office.
It was painful, but I relish the idea of walking someone through a GUI to do it even less.
How did you get the person to understand the concept of "what the command printed out"? I don't know how many times I had to say "Yeah, but look above the dollar sign, was there any text printed out between the current dollar sign and the last one?" The person I was talking to always would complain "IT DID NOTHING I'M BACK TO THE SAME THING."
I eventually got through it by getting them on IM and giving them text to copy-paste, and sometimes they'd send me screenshots.
Ori has it exactly right. Your mental model in seeing a CLI is that there are a series of commands being executed, that each one produces output, and that one adjusts what commands one executes in response to the output to achieve a goal.
Your user's mental model is that they are looking at a black and white screen written in ancient Aramaic. They can't read it, they won't try to read it, and they cannot keep it in their working set while speaking with you or while engaged in other tasks such as, most relevantly, typing. They hope the demon on the phone will tell them the right magic spell, because this is so frustrating.
But irrespective of their inability to read ancient Aramaic, they can still identify color, location, and motion. So the clever demon will always phrase his requests to read ancient Aramaic in terms of color, location, and motion.