I think there is a key difference between our situation and Adis's that we are missing. The Key difference is that, while he was a preist, Adis was ultimately a normal Pokemon up against supernaturally empowered entities and thus could not even consider assassination. As Emissaries, we are supernaturally empowered entities, we would be on even footing in a straight fight (to our knowledge) and could theoretically do a localized 'purify' or somesuch with what powers Mew gave us, methinks.

That being said, I'll defer to the majority. We know who she is and what she asked of us, though...Here's another good question, however. Do we tell someone so that she can be restrained in a county prison? Or do you think that such an act would be equivalent to killing her anyways?