V.B.
I think all kids go through periods where they don't sleep as well as they do other times. My thought is that she is trying to give up the morning nap and that is changing her routine, so it is interrupting her afternoon nap. I would just give up the morning nap entirely and run her hard during the day so that she will be really tired for the afternoon nap. Try to put her down around 1-1:30pm or when you see her tired cues starting (if you wait to long, she'll be overtired and won't sleep well). Once you get into this new routine, I bet she will start sleeping longer during her nap again. Good luck!