Because it won't really help; it plays into the scene Evans wants to cause. Even if she gets warned off through supernatural bullshit the other people like her would just gossip more and cause trouble for the members of our family invested in this community.If successful it will cause her not to talk to us or our siblings again, which is all I want out of this conversation.
Also who says our threats have to be insincere?
In my opinion the best sort of empathy based social combat is the sort that uses both aspects of the skill. So something that's on one level social leverage, but on another is still experiencing someone else's perspective when you act on it.
In this case, there are two levels you can interpret this course of action on.
The first (and primary in my opinion) is as an earnest attempt at reaching out and trying to be better to each other. Ideally this works, but from my experience catty church going hypocrites are basically white court vampires with honest engagement as a bane.
The other level here, that becomes relevant if she chooses not to interact with us in good faith, is the social combat metaphor. She tried to stab us with a word shiv; stabbing back hurts her, but it also plays in to what she wants and the scene she'd prefer to happen.
Instead, what I wrote in has us parry her and lead into a situation where we've got the implications backing her word shiv -specifically her alleged superior Christian virtue- against her throat.
We do this by calling out the difference between how she's acting and who she's implicitly claiming to be, then quoting a relatively obscure passage from the Bible to back up our point. That's basically the catty church social politics equivalent of a perfect defense with a free counter attack attached.
We let go of the knife by making the getting better part a mutual thing, but that just boxes in her future responses even further.
To be clear: the intent in my write in is as it seems in the text, not to play at cynical social manipulation. However, it's still worth considering the social mechanics in play.
Done this way we either get through to her based on sincerity, or we place her in a position where she has to choose between backing off and continuing to embarrass herself.
… this is probably the point where I've put too much thought into this isn't it?