She would appropriate the nails on the wall to her own uses, and lay Kate's clothes on Kate's trunk and let it go at that.

Any woman, Kate told herself, would resent such treatment.
Then Marion was always going off alone and never asking Kate if she would like to go along.

That was inconsiderate, to say the least.

And look how she had acted about climbing the peak at Mount Hough, the day they had gone to see the lake! Kate had wanted to go down to the lake--but no--Marion had declared that it was more beautiful from the rim, and had insisted upon climbing clear to the top of the peak, when she knew perfectly well that the altitude was affecting Kate's heart.
And she had gone off alone and stayed nearly two hours, so that they were almost caught in the dark on the way home.

It was the most selfish thing Kate had ever heard of--until Marion perpetrated worse selfishness which paled the incident.
More than that, Marion was always making little, sneering remarks about the professor, and doing little things to annoy him.