If Snape told DD about the UV, how would DD have responded?

[potioncat]

No: HPFGUIDX 137677

Carol asked:
[Suppose that Snape is in fact loyal to Dumbledore, that he realizes
he has been trapped by a combination of Voldemort's malice and his own
pride and folly (agreeing to take the vow and thinking he can slither
out of it through cleverness; not anticipating the terrible third 
clause.)

Suppose that he goes to Dumbledore and says something like,
"Headmaster, forgive me. I've done a stupid and terrible thing." And
then he tells the story, the true story with the complete vow and what
he saw in Narcissa's mind.

What, based on our canonical knowledge of Dumbledore, which we know
includes total faith in Snape, would Dumbledore have said to him?]

Potioncat:
For this post I am looking only at the fact that Snape did take the 
vow, and assuming that he knew that DD was Draco's
target--leaving other interpretations for different threads.

I think DD looked Snape squarely in the eye and asked, "Why did
you do such a thing? I haven't seen anything this stupid since you
went into the tunnel after Remus when you were a teenager."

Well, maybe not. 

Before July 16 we knew nothing about Unbreakable Vows, and now we 
know--not much more. It makes "read the fine print" pale in 
comparison, and it's beyond me why anyone would make an
Unbreakable 
Vow. I wonder how common they are in the WW. Apparently the twins had 
the ability to put one in force if Arthur was so upset by that 
incident.

Magic contracts are fairly common in fairy tales and folklore. Deals 
with the Devil are frequent themes and the hero, in spite of making 
an iron clad deal, always manages to out wit the Devil and go free. 
In those stories though, the hero usually stands to gain something by 
the deal. I'm not sure what Snape had to gain here. The one thing 
that happened, as someone said in another thread, is that these three 
made a deal that was actually going against LV, and started a small 
but visible crack in their loyalty to him. 

But, the question was about Dumbledore. Snape has put his life and 
Dumbledore's at great risk. DD has of course, put Snape at risk 
before. He also put his own students at risk by hosting the 
Triwizard Tournament. Risk to life seems to be an acceptable 
challenge in the WW.

Snape told Narcissa that he thought LV intended him to do the deed in 
the end. It's very likely (if Snape did already know about
"The 
Plan") that DD and Snape had discussed this too. Something along
the 
line of, "Headmaster, the Dark Lord has ordered Draco to kill
you. 
I'm sure he expects the boy to fail. At some point, he will order
me 
to take on the task instead. I believe this assignment is as much to 
punish Lucius as it is to destroy you. But at any rate, the Dark Lord 
is no hurry for me to make the attempt. For the time being I am more 
useful to him as a spy."

And, after some thought and a lemondrop, DD would say, "Voldemort
has 
made a poor choice. This may be the wedge we need to cause the 
Malfoys to break away from the Death Eaters, and if they break away, 
others will follow. Severus, do anything in your power to foster 
discontent in Narcissa's heart."

Then, some time later, Snape comes back and confesses that he has 
made an Unbreakable Vow with Narcissa. After some thought, DD would 
say, "This changes little, Severus. We already knew that you
would be 
ordered to kill me, and to fail would mean death for you. We have 
both been at Mortal Peril for a great number of years now. The Vow 
has made keeping us both alive a bit more difficult. But
Narcissa's 
wording leaves us some space. We will have to do the best we can. If 
fortune goes our way, we will have overcome Lord Voldemort before 
Draco makes a serious attempt on my life. And my boy, the magic 
protecting the Horcruxes may make the vow null and void any way."

>From this point, I believe, DD and Snape make and adjust plans as 
needed. I seriously doubt that they started out with a plan for Snape 
to kill DD. But as the year moved on, they would have had to discuss 
different options. And at any given moment, it would as likely have 
ended in Snape's death as Dumbledore's.