The Demi-Goddess known as Luna Pandora Lovegood was usually considered a very open minded individual, occasionally saying things that didn't make sense to most people. But even she had her limits when it came to very annoying people. Most of the time, she would simply either ignore them or say something that was amusing to her but very confusing to others and make them leave. The amount of people that could test the limits of Luna's patience was rather small and the most recent addition to that small list was the newest Defense Against the Dark Arts Professor. Dolores Umbridge.
Knowing her mate, Luna imagined that the titles Blake would use when either referring to and/or addressing the woman in pink would be either Worm and/or Pest. In fact, she probably wouldn't be surprised in the slightest if/when the newest DADA-Professor removed herself from the realm of the living and earned herself a so-called Darwin Award. Cause of death? Pissing off Blake Ophis Ouroboros! Luna had actually heard (admittedly only snippets) that there was already a betting pool amongst the older students regarding when Blake would kill Umbridge, not that Luna could really blame them considering how Blake made her annoyance with Ronald "the Cockroach" Weasley clear last year, killing Umbridge in anger (or more specifically/likely, retaliation) wasn't out of the question.
The fact that Umbridge, like most of the Wizarding World, was most likely ignorant about the Supernatural World and therefore didn't know who Blake's mom was made the odds of the woman in pink walking away with her life intact worse.