Seeing her in pain and shock like this was not particularly pleasing to Lucius. Never before had he felt compelled to harm her and he wouldn't have if it hadn't been for his damned arm. Even now though it did not feel right to do this to her, although he felt no guilt from his actions as such.
"I never wanted it to come to this" Lucius murmured as he drained Buffy, he decided to take enough to make her compliant enough once he was done so that she would actually stay and rest. She would only go and get herself hurt. When he was finished he placed his hand over the cut her had made and healed it so that not a single blemish remained. He then did the same to his own arm and it's burst capillaries and fractured bone.