I think you need to try the CN again and do the second nap 3hr after. I don't think you can count it out just trying one day. She's not likely to show tired signs as much because she's had a short sleep in the morning, just enough to get her through to a proper afternoon nap. My DD never really showed them either, I just put her in early one day and found the right A. It does sometimes take a bit of trial and error, but is really the best way to go if she's not quite ready for one nap.
(((Hugs))), these transitions can be tough!