It's just my opinion but I don't think its a foreshadowing that Shallan is the destroyer.
When you're ten, everything you know, everything around you, your family. They are your world, they are everything you know. You believe that you know how the world works now. And so anything that changes that 'world' that you're used to, any shifts in that perception, makes it feel like it's the end of the world.
To Shallan, maybe it was her mother's death, her part in the death, or even the deaths itself. Those things cause such a shift in her perception, such a discrepancy in her worldview, that it feels to her like the world has ended.
Ngl, Shallan is my favorite. And I will and can write whole papers on the complexity of her character and why everyone should love her as much as I do.
But I think I have gone off on a tangent so, TL;DR: I don't believe Shallan is the destroyer, or at least that sentence doesn't mean that she will be the destroyer.
Also, I'm probably thinking too much on this but the lullaby that her Father croons to her, am I the only one who thinks it could be something more? A way to Urithiru perhaps?