* Nagini was killed by Neville Longbottom in the final battle at Hogwarts, where she was still in Voldemort's possession.
* She was never hidden or discovered as a Horcrux throughout the book, unlike other objects like the locket or the diary.
It's important to remember that while the other Horcruxes were objects, Nagini was a living being. Voldemort used dark magic to turn her into a Horcrux, and it was not revealed that she had a particular location where she was kept.