GreatWhiteApeofBarsoom — 9 years ago(December 04, 2016 07:47 AM)

Joker was the thug who killed her father. Valestra obviously knew also given the dialogue between the two. I would guess Andrea did research on the mob underling who had killed her father and realized the Joker was that man. It didn't take Batman long to figure it out either once he suspected. I'd guess Andrea found out by similar means.
Requiescat in pace, Krystle Papile. I'll always miss you. Justice was finally served.