Nagini: If she's not a Horcrux, what the heck is she?

[mandorino222]

No: HPFGUIDX 171930

Carol wrote:

"and I can't see her as an attraction at the London Zoo." 

Nick says: 

I have no canon in front of me, but has everyone already rejected the 
idea that Nagini is the snake that Harry freed in SS?  Do their 
descriptions conflict with ne another?  It could turn out to be another 
example of Harry's mercy (freeing the snake) helping him in the end 
(snake turns on Voldy in critical moment because he owes Harry a favor, 
or something...)

Either way, I have issues with Nagini as a horcrux.  What happens when 
she dies of old age?  Or does LV give Nagini a horcrux as well 
(creating a horcrux within a horcrux, or something equally perverse)?  

If Nagini is a horcrux, I will be disappointed in JKR.