Ok this may be a dumd question (Snape/Lilly)

[Zara]

No: HPFGUIDX 182574

> Tandra:
> Ok so we know that Snape's Patronus is a doe, which we find out in 
DH. 
> But why does it seem to be common knowledge(to Harry, DD, and 
everyone 
> on this board but me) that Lilly's was a doe as well? 

zgirnius:
Within the books, the only reason we have to believe that Lily's 
Patronus was a doe, is that Harry says so to Voldemort in "The Flaw 
in the Plan".

> DH: "You never say Snape cast a Patronus, did you, Riddle?

<snip>

> "Snape's Patronus was a doe," said Harry, "the same as my mother's, 
> becaue he loved her for nearly all of his life, from the time when 
> they were children."

zgirnius:
The question of how Harry knew this, is not answered in the books. A 
couple of reasonable suggestions could be that Harry worked it out 
using logic - he knew Snape loved Lily, he knew Snape's Patronus was 
a doe, and he knew that Lily loved James, a stag Animagus. Or perhaps 
even, having worked out this possibility thgouth logic, he remembered 
the same of familiarity he had felt when he first encountered the 
doe, and decided this was because it represented his mother.

Rowling has, I believe, also confirmed that Lily's Patronus was a 
doe, and this represented her love for James, in interviews.