She's there to collect a bounty

Copperhead has been hired to kill The Joker for 45 million dollars Copperhead watches from her hiding place on the shadows of the ceiling The Joker is talking to a kid named Anarchy. They seem to he getting along talking about this city and how it's gone downhill she eventually grows tired of their chatter and drops down on top of Joker she goes to break his neck but he slips out and throws her as she lands on her feet

Joker: hehehe my my copperhead I haven't seen you in ages bet you thought id be a easy kill didn't you?