Lawler knew, and Lawler had helped her father.

And now, she was certain, her father had again fallen.
She steeled herself against pity for him, determined that she would not stand idly by and watch him betray Lawler.

She did not know what she intended to do, or what she could do, to prevent the stealing of the Circle L cattle; but she determined to watch her father, hopeful that she might devise some way to prevent the thefts.
She had passed many sleepless nights, having become aware that her father was habitually absenting himself after nightfall, but she had never been able to catch him in the act of leaving the cabin at those times, though many nights she had purposely stayed awake.
Tonight she had gone to her room, to lie awake on the bed, fully dressed.

She had left the oil-lamp burning, for Hamlin had been sitting at a table reading.

She heard him get up after a while; saw the light flicker and go out; heard her father cross the floor and go to his room.
There was a fire in the kitchen stove, for the weather during the day had been cold, and she could hear the embers crackling for more than an hour after her father went to his room.