Continuity mistake: Drusilla kills Kendra by cutting open her jugular artery and leaving her to bleed to death. When Buffy enters a while later, there is not a drop of blood anywhere. (00:41:40 - 00:42:45)
Continuity mistake: In 'Becoming, part 1' as Buffy kneels over Kendra's corpse you can see the door over her shoulder, it stays closed all the time. There is a cut to a shot of Buffy from behind showing a cop raising his gun, but he couldn't have come through the door without us seeing him in the last shot. (00:43:10)
Continuity mistake: The white outline drawn by the coroner does not match where Kendra's body fell after being killed by Drusilla.
Continuity mistake: When Joyce is being interviewed by the policemen at the house, you can see the number outside the house, but it says 163 instead of 1630, the number on which Buffy lives.
Continuity mistake: In "Becoming Part 2" At the end when Spike chokes Drusilla unconscious, he picks her up, one of her hands is resting on her stomach and the other is hanging to her side. It cuts to a shot of Spike looking at Angel and Buffy fighting then to Spike leaving with his back facing the camera. You can see that the hand resting on Drusilla's stomach moved to Spike's shoulder.
Answer: She has superpowers, ergo fast movement. The reason she outruns him so easily in "Touched" is that she stops trying to actually fight him and just dodges instead.
Shay