Calliope's nap put her at just about six hours after her last dose of Motrin, and well more than four hours after her last dose of Tylenol. She lasted another twenty minutes after she got up before getting cranky. I checked her temperature -- only 100.8! I followed that up with some Motrin, given the crankiness, but am cautiously optimistic.
Plus she ate a little yogurt for dinner, her first solids all day.
So I'm hopeful that the tide has turned and that this will be it for this fever (never mind middle of the night adventures with changing sheets and washing sleep sacks!).