Look, if Rooke doesn't show up down there, so that we know he's only philandering with Nan and has no real intention of marrying her, will you come then ?" He still hesitated.

And all at once Kitty saw the other side of the picture--Peter's side.

She wanted him at Mallow--they all wanted him.
But she had not thought of the matter from his point of view.

Now that she knew he cared for Nan she recognised that it would be a bitterly hard thing for him to be under the same roof with the woman he loved, yet from whom he was barred by every law of God and man, and who, as far as Kitty knew, regarded him solely in the light of a friend.

Even if Nan were growing to care for Peter--the bare possibility flashed through Kitty's mind only to be instantly dismissed--even so, it would serve only to complicate matters still further.
When she spoke again it was in a very subdued tone of voice and with an accent of keen self-reproach.
"Peter, I'm a selfish pig! All this time I've never been thinking of you--only of ourselves.