As I wrote elsewhere, the photographer has been bossy and mannish in spite of her sexiness to us. She's a tough cookie and respects money (licks her lips while Charley is counting it out) and roughness.
Plus, she's a bit S&M and recognizes that in Molly. He saw that in her and that's why he slaps her. Plus, to bring her down a notch.
Molly's probably really turned on, having just beaten Harmon to death. Note his lascivious glance at Jewell's ass as she digs into the fridge... she knows she's putting on that show, too.
Now, Molly has a chance to play out his sadism with someone who'll appreciate it!
I just hope Molly didn't kill her afterward. I liked Jewell!
(I know it's a movie, but these characters are so realistic)
I agree with what was said before re: Miss Fort. She has a chip on her shoulder re: Boyle's treatment of her, plus she doesn't often meet straightforward guys like Charley. Plus, his veiled threat to throw her out the window... either she's still under the threat, or she kind of appreciates his inner character and intelligence (tricking her with flowers, etc).
BTW "Sybil" is a witch's name, and she "holds the Fort" for Western Fidelity, the Mafia front corp. I like delving into the possibilities behind character names!
Maybe you're on to something with Jewel being into S&M. I think Molly was just letting her know in a direct way with the slap that he was in charge, he was the taker. The smile may be her way of saying..."you can have all you want, big boy." Better for her to go along, than to be brutally beaten and raped.
Also, the scene earlier with Molly in the whorehouse...he may have resented the offer. If the madam hadn't said to him 'he could have anything he wanted.' Molly could have...but for him, if he'd just grabbed any or several of the gals there and dragged them into his room....that's more in keeping of his character...the taker...and we see how that is part of his downfall.
I agree totally with Miss Fort...I don't think Boyle was much of a lover and certainly not a romantic. The flowers were a romantic gesture (why would Boyle ever bother? he was getting what he wanted from her. Also, as they go round the compass, Charley appears to be a better lover...she most likely rarely if ever got the big O from Boyle....so she has her fun with Charley. Plus, Boyle knows Varrick is there with her, yet he never asks about her welfare. Another way of showing her he could care less.