Just look at what Harleen/Harley is wearing in each segment. Yes, the armed men come in, shoot up the place & Joker tortures her but I don't think she becomes Harley then. I think he uses her to escape. Later when we see them (when she pulls the gun on him) she is still Harleen and conflicted as to doing the right thing (shooting the Joker) and loving him and he wins. He will then push her into the vat of acid, finalizing her transition to Harley. They will be at a club (see her dancing in the trailer wearing the same clothes/jewelry as in the car) when confronted by Batman, they escape and the car chase ensues. My opinion, anyway.