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.
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. The next time, she attacks him in Bathilda Bagshot's house and he literally has no time to speak, just desperately try to defend himself.
Nagini the Snake
Nagini was the last horcrux to be destroyed and also the last to be made. It was created when Peter Pettigrew bumped into Ministry of Magic employee Bertha Jorkins in Albania while Voldemort was still weak.
Her body disappears and gives way to Nagini, while Hermione finds what seems to be the snake's changed skin. Nagini's impersonation of Bathilda is, nevertheless, an intended trap by Voldemort for Harry, which might have put his most important Horcrux in jeopardy.
The unusual talent known as Parseltongue, which Harry possesses, is passed through a family bloodline. Given that many Dark wizards and witches, including Lord Voldemort, also possess this talent, it is regarded as a dark gift.
As J.K Rowling revealed, Albus Dumbledore had mastered Parseltongue too – although he could not speak it aloud. We're not sure why Albus learnt the language, but perhaps the Hogwarts headmaster wanted a better understanding of Voldemort.
Salazar Slytherin and his descendants were fluent in Parseltongue — the ability to speak to serpents.
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.
Lord Voldemort and Nagini had a special relationship
As a Parselmouth, (i.e. able to talk to snakes) Voldemort could communicate with her, and the pair often sent each other messages, even suggesting a telepathic connection at times.
Unless one or the other has a significantly smaller role in the films than we are led to believe, Dumbledore and Nagini will get to know each other. From the very little we see of Nagini, it looks like she's at least potentially on the same side as Dumbledore.
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'.
In a film extra called "Credence, Nagini and the Circus Arcanus," available on the "Crimes of Grindelwald" Blu-ray, Rowling said she "knew all along about Nagini." "Now, there were always hints that she had been human," Rowling said. "In her name — because the Naga are, in mythology, a race of snake beings.
Bertha Jorkins was the person who was killed to render Nagini as a horcrux. At the start of the fourth book, we find Voldemort and Wormtail(Peter Pettigrew) in the Riddle mansion.
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.
Why did Voldemort have Nagini kill Snape instead of doing it himself? Because he thought he couldn't do it himself. Voldemort was holding the Elder Wand, but thought that its true allegiance laid with Snape, as he was the one who had killed Dumbledore, its previous owner.
In the belief that the Elder Wand will grant its allegiance only to one who has slain its previous owner, Lord Voldemort has his pet snake, Nagini, kill Severus Snape.
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. Burbage is later replaced as Muggle Studies teacher by Alecto Carrow.
So it's possible that Nagini met Tom Riddle in his early years of rising to power but by the time she found him in Albania she had been cursed to become a snake entirely, and losing the ability to turn back into a human.
Nagini was a maledictus. That means that she carried an innate, hereditary blood curse giving her ability to transform herself into snake, which gradually became uncontrollable until Nagini eventually lost the ability to turn back into human completely.
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.
The second film in the series, written by Harry Potter architect, J.K. Rowling, revealed in a trailer that fans had been on the right trail. Nagini, it turns out, was actually a Maledictus—a witch with a blood curse that turns her permanently into a beast (in her case, a giant snake).
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.
Harry is the Heir of Gryffindor (though his powers have been bound by his father when he was a baby), Neville is the Heir of Hufflepuff, Meghan (OFC, daughter of Sirius) is the Heir of Ravenclaw. Harry/Ginny, Ron/Hermione, Remus/Tonks.
Ginny Weasley was able to speak Parseltongue while she was possessed by Tom Riddle's Diary, which enabled her to open the Chamber of Secrets.
Yes, he loses his ability to speak Parseltongue. In fact he lost the ability the moment Voldemort destroyed his part of his soul which lived as a horcrux ... And, yes, once the fragment of Voldemort\x27s soul that Harry contained was destroyed by Voldemort, Harry lost the ability to speak Parseltongue.