@lomie0: I don't think it's "plot damage", considering that the artist is making a point of not showing what the injury actually looks like, strongly implying that it's
very gory and probably reaching straight to her vitals -- which, considering that almost the entire torso is obscured, may very well be everything from her heart and lungs (definitely fatal) to her viscera. My guess is that healing magic only works if the target won't die within mere seconds of sustaining that injury (so for example, having your arm lopped off will kill you in
minutes from blood loss), possibly because the magic itself isn't instantaneous.
@Tyron: Hiya didn't attack Risu on purpose. Risu (who was standing at Fulio's side) simply interposed herself in front of Fulio to defend him (unnecessarily, but she had no way to know that he had an OP self-activating defensive shield) from an attacker that she had no way of knowing was way above her league (at least in her humanoid form).
@Invader_Retro: Not really forced. There was no indication that Risu knows of Fulio is protected by a magic barrier that is both uber-powerful and auto-activates at the slightest sign of an impending attack that can actually threaten his life.