Hi,
I have found a report in Scotsman 17 Sep 1834 of a "Melancholy Accident." She is reported Mrs Knox wife of the Land Surveyor, she was ran over by a StageCoach outside the "New High School" at 5:00pm on Monday 15 September 1834. I suspect the "New High School" is the building on Regent Road/Calton Hill area, which they are thinking of turning into a Music School.
A surgeon, Mr Millar was present but he was unable to save her. I can email thereport to you if you require.
I still don't think this is the Christian Knox you are looking for.
Tom