Why DD did not ask Snape to kill him. (extremely long)

[houyhnhnm102]

No: HPFGUIDX 166130

Carol:

> He could be bluffing, pretending to know Draco's 
> job, but the protections on Hogwarts, the interview 
> with Draco that Harry overhears, and Dumbledore's 
> attitude suggest otherwise.)

houyhnhnm:

What I wouldn't give to be able to log on to some 
kind of "Watch What Happens" after-the-show show 
for "Spinner's End".

When that "rope, like a fiery snake" cooled down, 
what happened next?  Snape couldn't very well say, 
"What is it  I'm supposed to do, now?" even if he 
didn't know Draco's task beforehand (as I believe) 
because he had already convinced the sisters that he knew.

But it is possible that he had gained enough of their 
trust by making the Vow to draw out Narcissa, at least, 
in the conversation that ensued.  Surely the two women 
didn't just get up and leave with no words spoken.