Buffy doesn't waste more than a second or two staring in shock; she's snapping orders, even while dropping to the ground to start trying to deal with the wound.

She's seen worse. She's taken worse.

(Hell, she's given Faith worse, and they're both still alive, right?)

The reception desk doesn't make for much cover. The huge Christmas tree, shoved over to land flat on its side with a musical crash of ornaments and lights, makes for slightly more.