Fuwawa's explanation for her r/w lisp is that she does it when she "gets excited." So when she always calls the ruffians "wuffians", or Nerissa "Newissa," it's because she's always excited when she talks or thinks about the ruffians and Nerissa. It's probably safe to assume CC is quickly becoming one of their closest friends in Hololive which is great to see, I hope they can do a proper 1-on-1 with her soon.