When Harry and Hermione are on the first floor of Bathilda's house, Nagini (inside the corpse of Bathilda) tells Harry to "Come!" from the next room in Parseltongue. In reaction, Hermione jumps and clutches Harry's arm, and the two of them obey the command.
Harry is never in a position to 'chat' to start with. She's there in the graveyard but Harry is surrounded by Death Eaters and Voldemort, he can't sneakily talk to her.
Harry being an accidental Horcrux meant he was bound to Voldemort in so many ways, just like Voldemort was bound to serpents. Not only could Harry speak the language of the snake, but could see through the eyes of Nagini, another of Voldemort's Horcruxes, as it turned out.
Because some snakes can sense heat and movement in a way humans cannot, Nagini was able to detect Harry and Hermione even when they were under the Cloak of Invisibility. Harry fought with Nagini, and the serpent bit him before coiling herself around Harry to hold him in place for Voldemort.
Though it may later be revealed that the Dark Lord did indeed know that Nagini was a Maledictus, there's currently no indication that he (or anyone else) ever thought that she was anything other than a snake who was made into one of the Dark Lord's Horcruxes.
Nonetheless, despite her initially benevolent nature, Nagini's blood curse eventually turned her into a snake permanently. Though it is unknown if she became evil as a result of that, or was turned evil as a result of Voldemort turning her into a Horcrux. As a snake, Nagini was completely loyal to Lord Voldemort.
Voldemort orders Nagini to kill Snape, and the great snake bites Snape's neck, mortally wounding him.
Dumbledore does not use any language to make one think that Nagini is anything more than a snake. But this could be despite his knowledge of Nagini's past because he has to factor his grand plans into everything he tells (or doesn't tell) Harry.
It wasn't just inanimate objects that could become Horcruxes. Lord Voldemort's beloved snake companion, Nagini, was also transformed into one, and Dumbledore seemed to know it, ominously predicting that a day would come where Voldemort would 'fear for his snake'.
Deathly HallowsEdit
Nagini, Voldemort's snake, then eats Professor Burbage's dead body. A story about her "resignation" from Hogwarts appears in the Prophet, but members of the Order of the Phoenix discount it, as they are unable to locate her anywhere after that.
Nagini is loyal to Voldemort because he can speak with snakes. As a Maledictus, there probably isn't much time after the events in The Crimes of Grindelwald before Nagini falls to her blood curse, becoming a snake forever.
In short, no one knows exactly how Nagini ends up as Voldemort's closest ally. Evidently, something happened between the time of her joining Newt and the events of Harry Potter that pushed her to the dark side. She might even have met Voldemort while still human, and he was Tom Riddle.
Fact: Nagini Is A Maledictus
A Maledictus, according to good ol' J.K., is a witch who has been born with a blood curse, carried on by her mother.
It is very possible that J. K. Rowling did say this, but that she was referring to the snake actors in the movies, not the characters. This is NOT true. The quote was started as a joke on tumblr. Besides, Nagini is a viper (a venomous snake), and the snake Harry set free was a boa (a constrictor, not a venomous snake).
Behind the scenes. When Harry and Hermione are on the first floor of Bathilda's house, Nagini (inside the corpse of Bathilda) tells Harry to "Come!" from the next room in Parseltongue. In reaction, Hermione jumps and clutches Harry's arm, and the two of them obey the command.
There was a rumour that Nagini was the snake Harry released from the zoo in Harry Potter and the Philosopher's Stone. This was proven false, as Nagini is some type of viper while the snake in the zoo was a boa constrictor. Furthermore, the snake was given a male voice in the film, while Nagini is female.
She was dieting and didn't want greasy food.
Harry Potter and the Deathly Hallows
In this book, Rowling reveals that Bellatrix is the guardian of Helga Hufflepuff's cup (though she is unaware that it is a Horcrux), which Voldemort has entrusted the Lestranges to keep in their Gringotts vault.
Voldemort, weakened by his long stint as "less than the meanest ghost' 69 insists on making one more Horcrux. And unlike with Harry, Voldemort did say the spell when he killed Bertha Jorkins to make Nagini a Horcrux.
J.K. Rowling recently gave more insight into one of the most controversial characters in the Wizarding World: Nagini, who was known only as Voldemort's snake in "Harry Potter," but appears as a woman in the prequel series, "Fantastic Beasts."
In the movies, Nagini was the one who killed Snape in the boathouse. The Maledictus meets her end when Neville Longbottom finds Gryffindor's sword and, in an attempt to destroy the final Horcrux, cuts off her head.
Because Nagini also happens to be the name of another iconic “Harry Potter” character — Lord Voldemort's magical, extremely murderous pet snake. Well, just in case there was any doubt, “Harry Potter” creator JK Rowling confirmed the two characters are one and the same.
Nagini seemed integral to Lord Voldemort's survival before he could be restored to his body, and we learnt, quite grotesquely, that Voldemort even tasked Wormtail to 'milk' Nagini so he could live off her venom to keep his strength up. BFFs forever.
He was given a Blood-Replenishing Potion, as he continued to bleed profusely any time his bandages were removed, suggesting that Nagini's venom somehow prevented or delayed blood clotting.
Therefore, when Voldemort used the killing curse against Harry in Deathly Hallows - Part 1, he was actually killing part of his own soul, and Harry was able to survive. And after Neville killed Nagini, all Horcruxes were destroyed.