I don't see that happening. There is definitely going to be an attack on the Expedition from this thing in the very, very near future. It was actively reaching out with magic designed specifically to throw a human wizard off its trail, aimed directly at Mathilde. You think after putting the eyeball on her that way that she can pretend 'I didn't notice anything' and it'll just let her walk off? Not going to happen. All we're deciding here is where the fight happens and whose initiative the fight happens on.
Sneak off to have the fight happen at the steam wagons, but on Chaos's initiative. Stand here to have the fight happen here, but on our initiative, not that of Chaos. It'd all a question of how valuable you think the initiative is. I value it a lot, which is why I'm voting to Stand Ground.
I think you're making assumptions here that aren't actually backed up by the text.
For one, you've asserted that the effect is Mathilde specific. It isn't.
It's cast on the mountain, not Mathilde and it acts on anyone looking at it. Now it is clearly aimed at Magic users (hence the message "stone is an excellent insulator of magic", but that is because no one except a magic user would be able to tell anything about the magic just from looking at the mountain. We're in Kurgan territory after all, and they almost certainly have their own (dark) magic users who pass by the mountain on a semi regular basis.
That would mean it is likely designed as a passive defence. Now, they might well still be observing us, but it will be at a distance, probably through non-magical means as I would expect that active scrying has a higher chance of being detected by the sort of people this field is designed to fool and "this uninteresting location is being actively scryed" is very suspicious.
In which case, if we start freaking out they might activate more active defences, but Mathilde is very good at holding a poker face, especially to someone who is observing from far away.
Secondly, that any attack will come right now. Again, if we don't spot anything (and all indications is that this is nearly impossible to spot), attacking us now would be foolish. They'll probably go after the expedition first, because we aren't wearing a "Lord Magister here" banner and it's the big prize the widow spent power on. They'll want to spend the element of surprise on ambushing the big prize, not the scouting party. In which case, not drawing away all the best protection from the caravan (most notably DEATHFANG) means it is better suited to defend itself until we can regroup here and defend both Matty and the Wagons.
