Henry James's novellaThe Turn of the Screwbelongs to the genre of Romanticism, particularly its darker "counterpart", known as Gothic literature.
Romantic and Gothic works in literature use realism in both, form and content. The themes are easy to identify for their crudeness, or by the way in which all the senses are appealed to, through the narrative. This is, partly, what conveys the realistic feeling of the characters, and of the topic.
The character of the governess is treated quite realistically, primarily because of her role in the story. In the 19th century, a governess did not enjoy the same reputation of modern-day au pairs to rich families. Far from the ideal of an educated, cosmopolitan, or well-traveled home-schooler, a governess was merely another family servant. Henry James's use of a governess as a main character is actually surprising, particularly to the very snobby Victorian London audience.
Another factor that makes her character realistic is that she is highly-flawed. As the main narrator, she tells us about the events from her own perspective, prompting us to create her portrait by ourselves. We can safely conclude, from her actions, that she is impulsive, prone to hysterics, and sometimes comes across quite over-dramatic in the way that she performs her role as the protector of the children.This is far from the image one makes of a heroine in a traditional novella.
What I then and there took him to my heart for was something divine that I have never found to the same degree any child—his indescribable little air of knowing nothing in the world but love. It would have been impossible to carry a bad name with a greater sweetness of innocence...
Even the most learned Henry James scholar has argued whether the character of the governess is real, a bit "off", delusional, sexually deprived, meant to produce humor, or even pity. This is because that is the precise feeling that Henry James intends to instill in us: the question of what is REALLY happening in that cold and isolated place. That brings out a lot of realism in the story, even when it is meant to be a ghost story.
[...] here, for many days after, it was a queer affair enough. There were hours, from day to day—or at least there were moments, snatched even from clear duties—when I had to shut myself up to think. It wasn’t so much yet that I was more nervous than I could bear to be as that I was remarkably afraid of becoming so...
Therefore, we can conclude that Henry James uses the Gothic elements of isolation, coldness, the supernatural, and agricultural depression to bring out the personality of a young, impressionable woman who has a very big responsibility, and very little help. The result is the creation of a realistic character whose flaws come as a result of what very-well could be extreme stress, a mental condition, or even the result of a haunting, depending on which perspective we choose to use, as the audience.