As far as I know, she is not familiar with Cox's Theorem at all, nor does she explicitly address the premise in question. I've been following her blog from the start, and I tried to get her to read about Cox's theorem two or three times. I stopped after I read a post which made it clear to me that she thinks that encoding the plausibility of a claim with a single real number is not necessary -- not useful, even -- to construct an account of how science uses data to provide a warrant for a scientific claim. Unfortunately I don't remember when I read the post...