Rebecca, much like Pepper, takes her job very seriously, but...

Rebecca, much like Pepper, takes her job very seriously, but she doesn't take herself seriously. A lot of actors don't like to play the fool. They feel it weakens them in some way, but Rebecca gets power from it. So when bad things are happening to Pepper, or humiliating things are happening to Pepper, she rolls with it. And because she's able to throw herself in all the way, it makes the gags work.