K.H.
Hi
I'm not sure I am reading your post correctly. Are you saying that she is tired and ready for a nap within an hour of waking from the previous nap? This seems like a lot of sleep in a short space of time and not enough wake time. She may have been doing this in the early weeks but it would seem to me that she is not ready to go back to sleep, her routine/nap time could be changing as she is approaching the 3 month stage. A yawn doesn't always mean they want/need to go back to sleep , I would wait it out for a bit longer and have her spend some time on her playmat while you play with your son.
Good luck
K.