Not much is known about Bianca's past. She and Nico were born before World War II, so Hades never broke the oath he took after the war to never have any half-blood children again.
Bianca and Nico both lived in Washington, D.C. at some point. When Bianca and Nico were very little, their mother, Maria di Angelo, died when Zeus struck the hotel they were staying in with lightning, trying to kill Nico and Bianca. The Oracle of Delphi showing up shortly after the destruction of the hotel, was cursed by Hades to never have her soul rest, and to stay in her body until it rots (and longer). He cursed her because she kept telling him that he should have given Bianca and Nico to Zeus as she knew their future.
Shortly afterward, both were brought to the Lotus Hotel by theFury, Alecto, who was disguised as a lawyer. Hades had to erase their memories in the river Lethe, so they wouldn't remember anything about their previous life.
After what felt like a month in the Lotus Hotel, which was actually about 70 years, they were taken out by Alecto. Hades wanted them because he wanted one of them to be the child in the prophecy.
Bianca is quiet and shy, and loves her brother, but dislikes caring for him all the time, and was relieved to be able to be her own person when she joined the Hunters of Artemis. She got along well with Percy, but he was angry with her when she joined the Hunters instead of coming to Camp Half-Blood, as this made him feel as if losing Annabeth had been for no reason at all and that she was also being selfish with Nico. He later forgives her, as she told him she joined the Hunters so she could live her own life and that she felt Camp Half Blood would be safe for Nico, for she believes that there are a lot of people like Percy there. Bianca and Nico both have a habit of gesturing with their hands while talking and when they are on edge.
Bianca di Angelo's fatal flaw may also (like her full-blooded brother Nico) be holding grudges. After her death, Bianca says that holding grudges is the demigod children of Hades' fatal flaw. In The Last Olympian, Nico tells his father that he (Hades), is holding a grudge that could end up killing the Olympians and the campers. It may also be a strong bond with those she loves (Nico). This may be because she was killed because she picked up a metal figurine of Hades, the only Mythomagic figure Nico didn't have, an act of misplaced sibling love.
I was amazed at how different she looked after just a few days with the Hunters. Her dark hair was braided, so you could actually see her face. She had a splash of freckles across her nose, and her dark eyes reminded me of someone famous, but I couldn't think who.
Bianca has black eyes that are like her father's, which gleam with either madness or genius, and silky dark hair. She is lean and about average height. She has olive skin, and used to wear a floppy green hat that hid her face. She gains the silvery aura all Hunters have after she pledges herself to Artemis, and doesn't hide behind her cap anymore. She pulls her hair back into a braid like the other huntresses. Her skin glows silvery, because of her being a Hunter.
In The Titans Curse, she is the only one who is able to kill the skeletons, which no one else could. It is highly likely that she was able to do this because of her father's power over the dead.
In The Battle of the Labyrinth, she (as a ghost) was shown to have dominion over the dead as they parted before her when Nico summoned her.
Presumably the other standard powers demonstrated by her brother.
She, Nico di Angelo, and Thalia Grace are the only Greek Half-Bloods of the Big Three whose aging has been tampered by their godly parent, which differs them from Percy greatly.
Bianca is the only known demigod to die on her first quest.
