And now she was witnessing or observing the complicated machinery of civilization through which they had come, at length to land on the beach of her island.

She knew now the supreme human energy which sent men to hell or carried them to their earthly heights.

Selfishness.
Supposing she saw the young man at dinner that night, emptying his bottle?
She could not go to him, sit down and draw the sordid pictures she had seen so often.

In her case the barrier was not selfishness but the perception that her interest would be misinterpreted, naturally.

What right had a young woman to possess the scarring and intimate knowledge of that dreg of human society, the beachcomber?
.