She saw their situation as he did.

The course of folly must be bravely taken, if taken at all: Disguise degraded her to the reptiles.
This was faced.

Consequently there was no fear of it.
She had very easily proved that she had skill and self-possession to keep him rational, and therefore they could continue to meet.

A little outburst of frenzy to a reputably handsome woman could be treated as the froth of a passing wave.

Men have the trick, infants their fevers.
Diana's days were spent in reasoning.