Eh, I don't know, since I didn't see exactly how everything went myself. But from what you've said, it sounds like everyone involved could have done better.
So, you and your boyfriend made a mistake, okay. You could have paid closer attention to the queue. But that doesn't give someone the right to yell at you. The woman could have made her case politely, not automatically assume you'd jumped the line deliberately and loudly called you out.
Your boyfriend's response may have been understandable, consider you two were being loudly called out for an accident. Still, telling someone to calm down is well known to make them even madder, so.
Your laughter didn't help either, as I'm sure you know, though it could have been a kind of embarrassed laugh or kind of in defense or your boyfriend or whatever, so possibly an understandable reaction to being yelled at in front of everybody.
So, maybe it was just one of those things and the employee only saw what they saw, and reacted accordingly. Maybe it would have been more fair if the employee had acted in a neutral way instead of taking a side, though.
Overall, I'd probably just consider it an unfortunate series of events and see if there's anything you could do differently in the future. Fortunately, there was no lasting harm. :)