What's Bred in the Bone by Grant Allen

When Elma woke up next morning, it was broad daylight. She woke with a start, to find herself lying upon the bed where she had flung herself. For a minute or two she couldn't recollect or recall to herself how it had all come about. It was too remote from anything in her previous waking thought, too dream-like, too impossible. Then an unspeakable horror flashed over her unawares. Her face flushed hot. Shame and terror overcame her. She buried her head in her hands in an agony of awe. Her own self-respect was literally outraged. It wasn't exactly remorse; it wasn't exactly fear; it was a strange creeping feeling of ineffable disgust and incredulous astonishment.

There could be but one explanation of this impossible episode. She must have gone mad all at once! She must be a frantic lunatic!