This is an on-going debate between my husband and I stemming from our viewing of Harry Potter and the Order of the Phoenix this weekend.
In OOTP, Umbridge really appears to be more of a misguided yes-man who is fully convinced that Harry and Dumbledore are trying to use scare-tactics to grab Fudge's position as Minister of Magic.
Fast forward to Deathly Hallows I (?), and her intentions appear much more malicious. At this point, she's aware of Voldemort's return and rising influence, yet she has Mad-Eye Moody's eye in her office door (or is this only in the book? I haven't had the opportunity to re-watch DH I or II yet). Either way, does this make her a death-eater? Or just stupid?