Caitlyn scowls. If it's random, that means there's nothing for her to figure out, no logic or deduction that can make it make sense. And, perhaps more importantly, randomness is much, much more difficult to stop.

"I thought you said in Dogtown that you were a queen."

She doesn't know what a temp is, or where Chiswick is, but she can guess from the context and Donna's tone that it's a menial job and a working class place. It doesn't change her opinion of Donna; Caitlyn's met queens, and she's much more impressed by Donna than by any of them. But she is curious.