Never, Why?
Who would've thought that the Slayer would be in that club that night? Darla certainly didn't think so. That was why she had gone. To get away from all the people who might have recognized her.
Not to say that she had. Certainly not when she had asked her to dance. Never thought to ask her who she was when she asked Darla if she'd liked to go back to her place. Definitely not when she had allowed Darla to chain her down and whip her.
Not when she had flipped Darla over strapped on a dildo and fucked her ass. Not when she was screaming her head in the throes of orgasm.
She only stopped to ask who Darla was after it was all said and done. When she told Faith the Slayer who she was, she never stood a chance.
Faith never stopped to ask her about anything when she rammed a little wooden stake through her heart. Not when she looked Faith in the eyes and asked why. Why? Why? Why?
There was no answer and there never would be.