In contrast to this natural beauty, she feels frustration towards her guide - an emotion which she 'does not love'. He is trying to protect her in an environment she where she sees only the beauty and not the danger.
In contrast to the natural beauty of the desert, she finds some towns filthy and her use of the word 'brittle' for the air suggests a harsh change in her mood, an irritation she can 'almost grind' between her teeth. She uses disgust to describe the town she passes through, evoking her attitude towards the 'fumes' that 'belched'. The continuation of the brutal, blunt mood she's in, where meat is 'butchered' - suggesting violence, 'blackened' by flies, a level of hygiene she seems to find shocking when she asks about the ancient Persian traditions of 'antibacterial agents'. Her knowledge of ancient culture shows that though she is educated in foreign customs, this place is foreign to her understanding. Though she is interested in it, her guide prevents her from following up on her curiosity.
When she uses the word 'penetrating' the desert, it suggests she feels she is breaking into something dangerous - but safe in the 'solid' car that reminds her of her husband. The repetition of 'so far' suggests that she is getting further away from him. Oddly, though, she says she is 'not unhappy' - but 'quite the reverse'. She says she is happy, despite the unhygienic horrors of the town and the frustration she feels towards her guide.
We can see…