This clip goes by in less than one second, but we see her facial expression change and fall from either a more neutral expression or possibly even a smile, and into that mouth gape.
I don’t think at the start of that change that she looks like a grieving mother looking for her missing daughter. I think this one second clip is possibly the exact moment she begins to realize that Luz even might be in trouble.
But considering the background clues seem to put her in the company of someone who knows about the Boiling Isles in some capacity, I don’t think she’ll spend very long worrying before learning either the truth or something close to it.
So, I don’t think she’ll get much of a chance to dwell on scary possibilities like “maybe Luz was human trafficked by drug junkies and murdered.” She might just get immediately thrown headlong into “your daughter went through a magic portal into a dimension of witch people”