The Ramseys owned John Douglas's book, Mindhunter. Even if neither of them had read it, they were obviously interested in true crime topics and would have known how important clothing fibers can be in solving a case. Regardless of whether Patsy had ever changed into her jammers or nightie and gone to bed, I think she purposely wore the same clothing on the 26th that she'd worn on the 25th to account for any of her clothing fibers that might later be found on JonBenet's body, and that the main purpose of her dramatic Lazuras bit was to provide an excuse for any such fibers. Too bad she didn't know that fibers from her clothing would be found in the ligature knot, as well as in the paint tray, which was still in the basement near where JonBenet's body had lain.
imo