It took me a while to remember since I'd read the chapter so long ago, but this is very close to the form she took when Magia Baiser corrupted her in her loss of control... Could she have actually been at least partially permanently corrupted at that time and we're only just seeing the outcome of that fight? She even bloomed into that form similarly to Baiser. Also as far as I'm aware, it seems only Enormeeta has those star insignias engraved on their body, but Magenta is now sporting them as well. I'm actually kinda excited for this situation beyond how fucking hot she got. Holy shit.
More like a burst of power. She just kinda had a big magical fart and destroyed the spooky ghosts.Magenta actually had a minor corrupted transformation in chapter 40 when she was with Alice.
I think there's one other thing that would support it; during the transformation sequence on page 19 the 6th panel shows an entirely different outfit silhouette before the Flower of Lust forms around her. So the residual dark magic from the 34-35 fight looks like it's overriding her real La Verita.Something that may support the idea that this is going to be a villain of the week thing and she'll get her real La Verita later is there's a reasonable chance that the shock will demotivate Baiser enough that she'll be in no shape to do anything. The rest of the Baddies will be off doing comedy with Baiser being in despair, which leaves the Magical Girls to deal with the fallout.