Livia does not know how to respond to that sort of self-deprecation—she has not seen it from Raylen for quite some time—so she simply doesn't respond.
She does not consider herself a particularly witty person. Unlike Raylen and Glynis, she tends to speak her mind directly and does not have the habit of making long-winded jabs at herself or others. She is also a lot less cynical and pessimistic.
This was something that made her feel insecure when she first started dating Raylen. He spoke so quickly and sharply to other people he was familiar with that she worried he found her dull. "I do not find you boring," he insisted when she fretted over this. "Sometimes I want to relax and unwind instead of being on-guard. And I can relax and unwind in your presence."
Of course, Livia wholeheartedly believed him then. She's not sure about now. His dry sense of humour seems to be innate and not something he has to put much, if any, effort into maintaining.