Draco Malfoy's mother Narcissa was cold, cunning and devoted to the Dark Lord. But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
Not knowing whether Draco was alive or dead, Narcissa chose to lie to the Dark Lord rather than risk losing her son. When Voldemort asked her to check if Harry was dead and she realised he was, in fact, still breathing, Narcissa seized her opportunity.
She asked him because if Draco was still alive, she had something to fight for. She had a reason to lie to Voldemort. If Draco is alive, she needs to get into the school to see him and protect him, and helping Harry feign death was the easiest way to do that. But if Draco was already dead, she wouldn't have bothered.
She checked his body, and felt the beating of his heart. Hands, softer than he had been expecting, touched Harry's face, pulled back an eyelid, crept beneath his shirt, down to his chest, and felt his heart.
Would they still have won the war if she had said Harry was alive? Harry could still defeat Voldemort because Voldemort didn't know that the elder wand belonged to Harry, so Voldemort would still be killed.
Draco's refusal to reveal Harry's identity to Bellatrix was not because he liked him. It was because he believed that Harry was the only chance they had at defeating Voldemort. At first, Draco admired and revered Voldemort until he threatened his family's safety.
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.
Actions have consequences – Draco learnt that the hard way. Harry would later risk his own life to save Draco from the Fiendfyre. Narcissa Malfoy would then lie to Voldemort – an extremely dangerous person to lie to – and spare Harry to hear that her son is alive.
She managed to leave without confrontation by simply not returning home to the manor again, instead going to live with her sister and their friends when not at Hogwarts.
Narcissa was taught the philosophy of blood purity from a young age and grew up prejudiced in favor of pure-bloods. Thus, like her sister Bellatrix, she cut off contact with her sister Andromeda after she was disowned and burned off the Black family tree for marrying Muggle-born wizard Ted Tonks.
In Cursed Child – Part Two, Draco Malfoy explains to Harry that his wife, Astoria Greengrass, was sick for many years. Draco says she suffers from a “blood malediction,” which ultimately ends up killing her the summer before Scorpius's third year.
In fact, Lucius' own support to Voldemort is revealed to come only under some form of duress, which is likely Narcissa's Veela Allure. When Lucius turns on Voldemort due to the reveal of his Horcruxes, Narcissa divorces him, taking 75% of Malfoy's wealth with her.
Though Narcissa may not necessarily have agreed with all of bellatrix's life decisions, and her views, she certainly loved her sister, and will have certainly mourned her death.
Only recently did I consider another explanation: that Lucius Malfoy is actually an emotionally abusive father, which manipulates Draco toward the Dark Arts.
Draco's father is a Death Eater. As a result of the big battle in the Ministry of Magic in Book 5 and as a result of failing to steal the prophecy of Harry from the Ministry of Magic, he's spending his time in Azkaban Prison.
Voldemort was scared it had gone wrong and was nervous to check. It was only when Narcissa checked that his arrogance returned. Only then he made up lies about Harry running despite all DE and Hagrid knowing that wasn't true.
Narcissa Malfoy's Very Dangerous Lie
But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
Isaacs brings up Lucius' disheveled appearance in Deathly Hallows, raising the possibility that the Malfoy patriarch had begun drinking too much. The way Isaacs saw it, Lucius was in a no-win situation. Given everything he'd done, the man no longer had a place on either side of the war.
She married Rodolphus Lestrange after leaving Hogwarts "because it was expected of her" to marry a pure-blood. However, Rowling stated in an interview that Bellatrix truly loved Voldemort.
It turns out that instead of rejoining the Death Eaters, Draco was supposed to help Harry at the very last second by throwing him his wand to help him defeat Lord Voldemort.
Harry Potter and the Deathly Hallows: Part 2: The Kiss.
He was more jealous of Harry than he let on
Specifically, Draco was jealous of Harry. It was easy to miss because Draco didn't often show his emotions, modelling himself on his cold, confident, calculating father, but J.K. Rowling has confirmed that a lot of his enmity towards Harry stemmed from envy.
Her sacrifice gave Harry the power of love, a protection spell sealed with the blood spilled by her death.
Though Harry encountered many opportunities that deemed Avada Kedavra necessary, it remains as one of the Unforgivable Curses Harry Potter never cast. For one, he viewed the spell as an immoral practice commonly used by users of the Dark Arts.
This theory suggests that each time he created a new Horcrux, that specific Horcrux diminished a part of his soul. Thus, his nose began to sink in, eventually disappearing altogether. Due to his tampering with dark magic, his human appearance evolved into a more snake-like state.