She offered the choclate right after she tried to give him the money. So, it was obvious that it wasn't the odd sweet tooth. She felt obliged to give him something in return, as if she was feeling bad about Shiek paying for a dinner that he wanted to pay for. It's not like Shiek's co-workers held a gun at him so he can pay for the whole thing. He was trying to be nice, and just a lovely gesture. She could have paid for his dinner next time or just got him choclate without trying to give him the money.
I know what you meant, I was kidding. But like I said, there is nothing offending in this at all, I would act the same way as she did with someone I am not close too, it would be ugly to reject joining Sheik's dinner when everyone accept, she felt she should do something in return, paying money wasn't really a good idea thou.
I wouldn't care much to these small details, everyone is different, think/act different, but I totally understand her. I don't know if you Lebanese say it this way, here they woould "ma bheb shil mnniyet haddan". Do you know what that means?