She certainly is busy fussing with the pebbles in the next right now. The chicks are exposed, but the wind isn't ruffling them too much, as they are much closer to the surface of the ledge.
Ah, now she's setting back down on them again after some house-cleaning.
It looked almost as if she was using nest pebbles to build a wind-break around the chicks, but I'm sure that is my human brain talking . . . is that far-fetched in terms of falcon behaviour?