Thanfiction's description of Diana; "Diana was about 5'8", stocky but not curvy, just kind of blocky, with what her mother honestly called "not unpretty" features, permanently sunburned cheeks, a slightly too-straight nose that she tried to insist was "Classical," medium brown eyes, and very thick, coarse, straight hair a little shorter than shoulder length that wasn't quite brown and wasn't quite blonde."
According to thanfiction:
"The look she got when she announced with absolute heartfelt seriousness after [[[Ernie Macmillan|Ernie]]'s and Neville's] flogging, 'It was abhorrent beyond words! Each rubied spatter on the cruel stones tore gems of sympathy from my eyes until I thought I would die from weeping!' Er...um...yeah. New girl officially very weird."
While in the DA, her fighting skills depended on her concentration. Sometimes she could be very good, or other times she could be way off.
She planned to marry someone wealthy and noble but refuse to enter the petty games of high society, working in a simple attire but with "an elegant spirit" to help the poor. For this reason, she loathed Susan Bones, whom she saw as everything that Diana wanted to be, with good looks to boot.
At her home in Leeds, she had many friends. She was popular with the other girls because she was a ringleader and a great storyteller. She was the one where picnics in the Moors was instead a tea party as Tiania and her Faerie Retinue.
She was starting to grow out of it before being forced to Hogwarts during the Year of Darkness. It was Diana's first year there--she was taught at home before then. She hated the school and the evil going on, but joined the DA because otherwise she was siding with the forces of evil. However, she threw herself into her fantasy world, reframing a lot of what she was going through as a way to cope. For example, training under Rowan became "toiling under the slavemistress". It came to the point where the lines became a little blurry on a few things.
She was killed in the Final Battle by a Reducto hitting her in the torso.