Umbridge Under the Influence: Dolores and the Locket

[Ceridwen]

No: HPFGUIDX 174743

What effect did the locket horcrux have on Dolores Umbridge?  She was 
the most horrible character invented in the series, so it's hard for me 
to see any difference between the High Inquisitor of Hogwarts in OotP, 
and the High Inquisitor of Muggles in DH.  She's still a rotten... 
person.

We know the locket exacted a toll on the trio when each of them wore 
it.  Tempers flared, spirits were depressed, and Ron's concerns seemed 
to have been magnified - shown in detail in the sequence where 
he 'kills' the horcrux.

What was its effect on Umbridge?  Did its influence weaken her 
Patronus?  Did it make her even eviller than she was?  Did it in any 
way influence her to retrieve Mad-Eye Moody's eye when he was killed?

At which point in the book, or the last three books, did she get this 
Horcrux?  How long has it been affecting her?

Ceridwen.