Continuity mistake: In the previous episode when Damon and Caroline sleep together Caroline's bra is dark pink, in this one when she wakes up her bra is blue.
The Night of the Comet - S1-E2
Continuity mistake: In the scene where Vicki wakes up from her nightmare her bandage on her neck is on the right, but then in the scene where she's at the Grill it's on the left side.
Continuity mistake: The sign by Mystic Falls cemetery says it was established in 1792, but later episodes state the town was built in the 1860s.
Answer: Because Lily's humanity was not turned off as Elena and Stefan's were...therefore she had some control over her actions and had a conscience whereas the other two did not at the time.