Suggest you start by taking her out as a passenger, you drive and give a running commentary of what you are doing, where you are looking, what you've seen, why you position the car where you do coming up to a bend, why skid marks suggest you exercise more caution on this bend/approach to a concealed entrance etc
This will not only give her insight and get her thinking/looking but it's actually good for you too, you might learn something yourself
Then you need to teach her the basics of car control to the point that she doesn't need to think about them, so she can concentrate on what's happening on the road outside the vehicle.
That's a lot of driving around a flat supermarket/showcase cinema car park without touching the throttle. Extreme clutch control, getting it to move just on tick-over revs (should be easy with the big diesel) and gently adjusting 'road position' with simple smooth movements that don't require crossing the hands.
Once she's mastered that, then go for acceleration and changing gear.
Once she's ok with that start with the observation of surroundings questions to get her to take notice of what's going on around her - "what colour car did you just pass on the left", "what just drove past in the other direction" etc. She doesn't need to be mastermind but spacial awareness and anticipation are what separate an average driver from a great one, the sooner she gets into the mindset that stuff really is going on outside as she fumbles with the gears, the better.
Only then would I venture out onto the open road - there's so much going on, with pedestrians, children running around, people driving and texting, overcrowding etc that I'd want to make sure she's confident enough to handle the car and generally see what's happening around her under 'normal' circumstances, before putting her into an environment where anything can happen, don't forget you've not got the benefit of dual controls, if she panics there's very little you can do about it until after the impact brings the Landy to a halt, and hopefully that's not parked on top of a bus queue.