Clues to Snape's Loyalties

[finwitch]

No: HPFGUIDX 170879

 "Kelly":
>

> 
> I was re-reading the books to get ready for next month and something
> stood out to me that I didn't think of before.  In GOF, when Harry is
> trapped in the office with fake-Moody, Snape's face shows in the foe
> glass.  Now, this may be nothing, but if Snape were really a Death
> Eater, wouldn't he be friend, not foe, to Barty Jr.?  

Finwitch:

That depends on how the "foe glass" works, actually Barty Jr. did not
own them, nor the Dark Detectors. As you'll recall, the Dark Detectors
were continously going off... because Barty Jr. was REALLY
untrustworthy to Alastor Moody (who did own them).

Maybe it shows the enemy of the one looking into it - much like the
Mirror of Erised... It shows Snape to Harry. Because he thinks Snape
as enemy or because Snape IS the enemy?
OR who Moody thinks is the enemy? (Alastor doesn't trust Snape, does he?)

Maybe the Foe Glass says as little truth of your enemies as Mirror of
Erised.

Question: Why Did the DA not see Umbridge in a Foe Glass?

Finwitch