Umbridge Secret Motive

I always thought Trelawney brutal sacking attempt from Umbridge was highly suspicious. Since Voldemort was after the prophecy that year, why not also try to get the person who made that prophecy as a plan B?

I don't believe Umbridge is a Death Eater, but she certainly has many things in common with them. Since she's at the Ministry, probably close with Malfoy, who's close to Fudge as well. So associating her with the Death Eaters was because once Voldemort would take over (in the 7th book), she keeps her job at the Ministry and maybe get some promotion. Send Dementors to Harry was maybe what triggered Vodemort interest for her, or maybe she did it upon Voldemort's orders, I'll have to think about this. What interests me is why she did it.

Sacking an incompetent teacher was serving the Ministry as well as creating a nice cover to get her banish from the Hogwarts grounds and therefore making her very vulnerable to the Death Eaters.

Now that I think of it, it should have been Snape instead of McGonagall, since he's the spy. Anyway