Yes she was.
She wasn't born that way; Voldemort made her.
Nagini the snake was the last Horcrux to be be created and destroyed.
The last Horcrux both to be made and destroyed was Nagini.
Neville Longbottom destroys the sixth Horcrux, Nagini, Voldemort's snake, with the Sword of Gryffindor during the Battle of Hogwarts.
Neville Longbottom( he killed Nagini)
Wherever Lord Voldemort ordered her to be since she was Nagini.
The last remaining horcrux was the snake, Nagini. Neville destroyed it with the Sword of Gryffindor.
THE FOLLOWING IS A SPOILER. IF YOU HAVE NOT READ THE BOOK, DO NOT READ (THE FOLLOWING)!Nigini is a horcrux, a part of voldemort's soul.
nagini [voldemorts pet snake]
There are no direct references in the books to Nagini killing a muggle out right. She consumed Charity Burbage after a killing curse was used on her and Nagini was made into a horcrux after her master killed Bertha Jorkins.
Lord Volemorts horcruxes included: - Tom Riddle's Diary - Slytherin's locket - The ring - Helga Hufflepuffs cup - The diadem of Rowena Ravenclaw - Harry Potter - Nagini the snake
There are seven horcruxes: Tom Riddles diary, Marvolo Gaunt's ring, Helga Hufflepuff's cup, Rowena Ravenclaw's diadem, Salazar Slytherin's locket, Nagini (Voldemort's pet snake) and the part of Voldemort's soul that is in Harry Potter. Then there is the eighth part of soul that resides in Voldemort's body (this part of soul does not count as a horcrux). However, Nagini was made a horcrux after Tom Riddle's Diary was destroyed so only six horcruxes ever existed at once (Nagini was made a horcrux with the murder of Bertha Jorkins in the sixth book).