I was talking in general...although I am not sure Camilla always walks a step or half step behind the King. Never paid attention to it.It would be hard to always do that in all the occasions as you are milling about
The Queen did not have to walk behind her husband when he was Prince of Wales, and she isn’t yet used to doing so.
One of the most basic principles in all of this protocol is “If no offence is intended, none should be taken”. Nobody expects her - or anybody else - to have instantly got used to all of this.
In time, I expect she will fall into the habit.