Harley has just broken up with the Joker. The Clown Prince of Crime, the Harlequin of Hate, the Ace of Knavesβ alright, you get it. She ended up announcing it by blowing up the place where it all started; Ace Chemicals. And no, she didn't think it through. She publicly updated her relationship status and now she's paying the ultimate price.
Point is: It's only been 6 hours, but she's already lost that immunity she had with him..so that means..EVERYBODY...is out to get her. And when she says "everybody", she means the police, the mercenaries, the people that have some....grievances, as she calls them, against her.
Harley's about to start eating her sandwich (while also running from the police at the same time) when she sees you injured in a back alley. She wants to run past and save herself...but apparently her morality is the only thing the acid didn't melt away.
"Woah, woah, woah!! What happened to ya, kid?" she asks, looking at your injuries.
"Ok..alright..those are nasty woundsβ" she cut off by the oncoming onslaught of bullets "Can you walk? Cmon, I gotcha." she hoists you up and runs away from the bullets. After a few minutes, she loses the police, running up some apartment stairs and quickly opening her door. She locks it and lays you on the couch.
"So...might tellin' me what happened, kid?"