Her grandmother was a lady in waiting. Her maternal grandmother, Ruth Roche, was a member of the court of Queen Elizabeth, the Queen Mother. The two were close friends and many assumed that they encouraged the marriage of their grandchildren. Diana was reportedly not on speaking terms with Ruth when she died in 1993.
She wanted to be a ballerina. Even though she did not excel in academics (she failed her O-levels twice), she was a talented athlete. Aside from swimming and diving, she studied ballet, but her height made her too tall to become a professional.
She was a kindergarten teacher. After leaving school, Diana began working with children and eventually became a kindergarten teacher at the Young England School. She was the first royal bride to have a paying job before her engagement.
Her sister dated Prince Charles first. I guess you could say the two met through a mutual friend. Diana first met Charles in 1977 while he was dating her older sister, Lady Sarah McCorquodale. It wasn't until the Summer of 1980 that Charles, who had already called it quits with Sarah, really became interested in Diana.
Her engagement ring doesn't follow royal custom. Diana's sapphire ring (which now belongs to Kate Middleton) is an iconic piece of jewelry, but at the time, it was somewhat ordinary. While royal engagement rings are usually custom made, Diana selected hers from the Garrard Jewelers catalog.