Should

What do 'think be supposed to' and 'should' mean here?

Getting out of the cab, I fumbled with my key and it fell into a puddle at my feet. As I bent to get it, a white hand flashed out and grabbed it before I could. I jerked upright. Edward Cullen was right next to me, leaning casually against my truck.

"How do you do that?" I asked in amazed irritation.

"Do what?" He held my key out as he spoke. As I reached for it, he dropped it into my palm.

"Appear out of thin air."

"Bella, it's not my fault if you are exceptionally unobservant." His voice was quiet as usual ? velvet, muted. I scowled at his perfect face. His eyes were light again today, a deep, golden honey color. Then I had to look down, to reassemble my now-tangled thoughts.

"Why the traffic jam last night?" I demanded, still looking away. "I thought you were supposed to be pretending I don't exist, not irritating me to death."

"That was for Tyler's sake, not mine. I had to give him his chance." He snickered.

"You ... " I gasped. I couldn't think of a bad enough word. It felt like the heat of my anger should physically burn him, but he only seemed more amused.

"And I'm not pretending you don't exist," he continued.

"So you are trying to irritate me to death? Since Tyler's van didn't do the job?" Anger flashed in his tawny eyes. His lips pressed into a hard line, all signs of humor gone.