For some reason he had decided to lock the door on the past, and the polite friendly indifference with which he had treated her was intended to indicate quite clearly the attitude he proposed to adopt.
She supposed he repented that brief, vivid moment in the car, and wished her to understand that it held no significance--that it was merely a chance incident in this world where one amuses oneself as occasion offers.

Presumably he feared that, not being a woman of the world, she might attach a deeper meaning to it than the circumstances warranted, and was anxious to set her right on that point.
Her pride rose in revolt.

Olga Lermontof's words returned to her mind with fresh enlightenment: "I shouldn't allow myself to become too interested in him, if I were you." Surely she had intended this as a friendly warning to Diana not to take anything Max Errington might do or say very seriously! Well, there would be no danger of that in the future; she had learned her lesson and would take care to profit by it..