Harley's eyes are moving rapidly and she is twitching. As Tiffany tries to give her the liquid the only thing going through her mind is the Joker is trying to get her to drink his Joker venom. The poison that makes you die laughing and then causes your face to stretch into a terrible smile after you are dead.
"No...NO!" Harley screams as she tries to hide under the table. "Lois? Where are you Lois? Please help me! I don't want to laugh any more! I don't want to laugh!"
Gaining a brief moment of clarity from the drug flashback, Harley looks up and realizes it is Tiffany trying to hand her the liquid. With a shaky hand she takes the bottle and quickly downs it before she slips back into another flashback.