Why should she conceal what she felt?
She knew it was a foregone conclusion.

They loved each other, and she would certainly marry him in the course of a year.

The long pent up forces of her nature were beginning to assert themselves; she had conquered and fought down her natural being in the effort to be all things to her old husband, to quench her growing interest in Giovanni, to resist his declared love, to drive him from her in her widowhood; but now it seemed as though all obstacles were suddenly removed.

She saw clearly how well she loved him, and it seemed folly to try and conceal it.

As she sat by his side she was unboundedly happy, as she had never been in her life before: the cool morning breeze fanned her cheeks, and the music of his low voice soothed her, while the delicious sense of rapid motion lent a thrill of pleasure to every breath she drew.