Pride and Prejudice depicts Jane Austen's keen interest in human relationships. How does she give a realistic touch to it?
Even though many people feel that Jane Austen is a fluffy writer that doesn't really deal in real problems that humans face, she actually creates quite a bit of real depth in her interactions between people. She makes the relationships seem very real and relatable in two ways. First of all, the characters that she creates are very real, meaning, they have flaws and weaknesses just like everyone else does. Even her protagonists always have weaknesses that they struggle with throughout the course of the book: Elizabeth was prejudiced, Fanny was overly shy and insecure, and Anne is too submissive and demure. By giving her characters flaws, that makes them more real. We like them better as a result, and it also creates more real situations. Elizabeth's prejudices get in the way of her happiness for a very long time. So, all of the interactions in the book, between people, are tinged with the characters' flaws, and that makes the dynamics very real.
The second way that the human interactions in the book have realistic tinges is that she portrays both good and bad situations. Not everyone is married happily ever after. Not all of the family members love each other without ever fighting or getting annoyed with one another. Men betray women, and women settle for less than they want. Every single human interaction, until the inevitable end that has a wonderful wedding and happy-forever feel to it, is filled the flaws that human beings possess. Austen didn't shy away from relating some of the more negative human situations; people eloped and committed affairs, friends fought bitter battles, families broke and feuded, and scandals were at every corner. That is like real life. Real life isn't some happy fantasy land filled with lollipops and rainbows. Bad things happen. People get angry with one another. And Austen did a good job of realistically portraying all of those situations.
I hope that those thoughts help to get you started; good luck!