Diana is the first born child of an accountant, Dwight Sharpe, and his wife whom was a local nurse, Carina. They were very young when they first had her and the family went through a number of financial troubles because of it, but Diana herself was never bothered by this too much - she was always able to entertain herself as a child with the most mundane of things and was rather quiet and modest, never really asking for anything. She never gave much trouble to them and they were appreciative of the fact.
Of course, this took a bit of a turn when the seemingly normal girl started to display strange powers as she grew up. Her parents were horrified of this and only wanted their daughter to be normal, but the idea of having her sent out to dormitories to receive a mostly free education weighed in heavily on the couple due to their financial difficulties. They ultimately opted to send her to Tallygarunga. Ironically they had their second child at roughly the same time, so this did little to actually improve their monetary problems.
Diana was enchanted by the wizarding world, no pun intended, on first sight. She knew that was the world she wanted to live in, what she wanted to explore and immerse herself in, what she wanted to die by. However, fate conspired against her - her parents both received promotions and bonuses, and steadily they saved up enough to rip Diana away from the 'blasphemous' education she was receiving just as she ended her fifth year in Tallygarunga. She was torn away from her life and her best friend and placed in a Muggle high school instead, much to her dismay. She was also forbidden to refer to magic in any way, practice it, or keep in touch with her fellow peers (which she did, regardless, since they couldn't do much about it to begin with).
Always having had an eye for prediction, she took it in stride and did her best in the Muggle school (a lot of knowledge which she was lacking, and had to 'cheat' her way through various tests, given that Tally never taught such needless things). While she was passing through the years she made an effort to fit in by writing for the school newspaper, and eventually for the local paper so to save some money to eventually leave. She didn't need that much at all, fortunately, since the stay in Tallygarunga was free and that was her first objective.
As she came of age, her brother started to display magical abilities of his own. She knew that their parents would not allow him to nurture that talent so it was finally time to take action. Instead of enrolling in college, like her parents wanted, she tampered with their memories to erase their children from existence. Added to that she also tampered her way into having her brother under her legal guardianship. With those issues out of the way, she took him all the way to Narragyambie overnight and enrolled him in Whitlam Bilby, while she herself returned to Tallygarunga to finish her education.
Her best friend had let her stay in his place after she graduated, so she could get her bearings - having a little money leftover, she managed to pay her own way through VMU while letting her brother live in Tallygarunga for the time being. It was in VMU that she met the one she believes to be the love of her life. For once, away from her parents, it felt like her life was finally starting to make sense.
Unfortunately the object of her affections began a relationship with Diana's own best friend instead. It seemed that life was throwing another curve ball at her - but at least she didn't actually hold any ill will towards them, unlike she did with her parents. Leaving them to do their own thing, Diana managed to move out and secure a small apartment in Melbourne for herself (and for her brother, of course, whom now finally had a residence that wasn't a dormitory if he so wished). She fully plans to throw herself at her job and ensure her sibling doesn't have to face half the problems she had to face on her own, and money solves a whole lot of troubles, now doesn't it?