Daelora Targaryen is a Valyrian princess, just like her siblings, but she is not a legitimate child. Unlike them, she was adopted by Queen Alicent Hightower and King Viserys I Targaryen, because her birth mother, Daenolla Drennaris (a runaway, noble-born Tyroshi lady), was raped by a prince, then the prince abandoned her. Daenolla and Alicent were close to each other (she was Alicent's lady-in-waiting), so she was beside her during her labour. Although, Daenolla didn't survive the birth of her daughter, she died few hours after. Ser Otto Hightower wanted to give the baby girl to other noblewoman, but Alicent took in the orphan girl and raised her as her own.
Daelora became a woman grown, a princess who is a force to be reckoned with. Since she was younger than Aegon, she hadn't threatened the order of inheritance, so Otto let her live. Daelora was taught how to fight with a sword, was foreign languages and war strategy, as well as had a dragon, a fuschia and golden colored dragon named Aeksilla (the name of the dragon means lady in Valyrian). Also she piqued Aegon's twin brother's, Aelon's interest.
The story does NOT follow the plot of the TV series House of the Dragon and the plot of the novel Fire and Blood!!!