When she realized the coworker (and, I realized later, her manager) were watching, she started laughing hysterically and said, ""Yeah, I took her $3. She caught me. I'm trying to steal a whopping $3 from her." as if I was unreasonable for wanting me measly bit of money back.
Yeah, but you shortchange every customer who comes through your till, and it can add up to quite a bit at the end of the week... 
The "measly" was perceived on my part. She made a few comments about I "must need a few bucks pretty bad" to make such a fuss over it.
You know, I've never understood the stories you hear about customers demanding that workers be fired. I have always thought that they were massive overreactions. Not anymore. I am not so much amazed by her behaviour as by the fact that she continued to be rude in FRONT of her manager and the manager said nothing!
It was such a downward spiraling meltdown that I don't think either of the other people in the drive-thru area knew HOW to react. The change debacle, which ended in the rude attendant's coworker scrambling to open the drawer to hand me my change, was followed by Rude Attendant handing me my bag of food. I checked the bag and saw my sandwich, so I pulled away, only to hear, "WAIT!" Rude Attendant had put my sandwich on top of items that belonged in an order the other employee was putting together. I had to hand my bag back to Rude Attendant so she could straighten it out.
Rude Attendant shoved the bag toward me. I took it, without checking it (my fault), because I just wanted to get out of there. The person, who I later realized was the manager, had this shocked, deer in headlights look on his face. Like he couldn't believe what he was seeing. And when I got home, I realized that Rude Attendant still ended up giving me the wrong bag. I ended up with my sandwich, another sandwich, missing side items from my order, but with side items remaining from the other person's order.