She looks like a Harley Quinn that's more worried about paying her mortgage than committing any weird crimes.
So we know this movie is about two characters, The Joker and Harley Quinn. Well I happened to have read the script and no spoilers but I can safely say there's a third character in this movie by the name of New York City!
But this time, the stair dance happens in Thailand - and its growth you see because now Harley Quinn does it with him.