Get a book on how to play folk guitar and go through it with her. It will have a logical progression of lessons and will give her something to refer to between lessons.

Why did you start with C? The C chords are difficult. I asked my guitar teacher why I had such a hard time with C, and he said, 'You're not supposed to play C on the guitar.'

Better yet, tell the landlord you would love to help but are unqualified to work with someone so young. You worry that you might strain her delicate hands and arms. It would be true.