Della Lu is a character in 2 novels by Vernor Vinge
, The Peace War
and Marooned in Realtime
She is an Asian woman born in San Francisco in the mid-21st century. In The Peace War she is an agent of The Peace Authority who specializes in counter-insurgency operations. Basically an idealist who believes that any methods are excusable in the service of maintaining "the Peace", Della has been ruthless in squashing rebellions in Mongolia. In the Peace War story, in 2048, she is given command of the Peace Authority's campaign to destroy The Tinkers in California and find Paul Hoeller, their leader and the original inventor of bobbles. She infiltrates the Tinkers, assisted by Miguel Rosas, who she manipulates through his hatred of bioscientists. In one of the most unrealistic (in my opinion) scenes in the book she and Miguel eventually sleep together, though they still consider themselves enemies after Miguel goes back to helping the Tinkers.
Della Lu is present at the Peace Authority's main headquarters in Livermore when the Tinkers attack, trying to bobble the Livermore bobble generator and render the Peace Authority basically helpless.
Della helps to defeat this effort, but her superior, the half-mad Hamilton Avery, thinks the Peace Authority is still about to lose. He is just about to launch Operation Rennaissance, which will basically set off nuclear armageddon while bobbling the Authority's main bases so that they can emerge in the future to take over the world again. Della's morality finally makes her change sides and save the day - she bobbles the Livermore base, and herself, but stops Avery from launching the nuclear attack.
50 years later, Della emerges from the bobble and somehow survives the wrath of her fellow Peacers, with the help of Mike Rosas, who has also bobbled forward in time for just that purpose.
She and Mike get married and become famous in a series of space exploration missions to the outer Solar System. Mike is killed during a mission to "The Dark Companion" (an object that Vinge never gets around to explaining). Stricken with grief, Della signs up for a solo mission to Gatewood's Star, a 1200-year round trip (most of that time spent in stasis inside of a bobble). She leaves in 2202, and returns in 3400 to find the Earth deserted, humanity gone, except for the few other travellers who used bobbles to travel forward in time. They had all missed The Singularity.
Della wanted to find out what had happened, and she thought that if she travelled the universe long enough she would find another intelligent species that was pre-Singularity, and she could find out what the Singularity was. So she left earth again for 50 million years. In Vinge's post-21st century universe, medical technology has reached the point where humans are basically immortal. Della becomes one of the longest-living humans ever during her travels, spending 9000 of those 50 million years in realtime. She never finds what she's looking for, though she does locate the ruins of 2 other civilizations. She returns right at the beginning of the book "Marooned in Realtime".
In this story she helps Wil Brierson in an investigation into the murder of Marta Korelev, who someone caused to be left behind while everyone else in the last human settlement bobbed forward 100 years. At this point Della is immensely powerful, having lots of high-tech weaponry and an advanced interface between her computers and her brain. At the beginning of the book she is also not quite human anymore, having spent 9 millenia alone in space. In the company of the humans again, working with Wil to solve the case, she gradually returns to a more normal personality. At the end of the novel she protects the settlement from another ancient and super-powerful human from the far past, and then returns to Earth and to Wil Brierson.