Any time she takes a really short nap, try to extend for 10 mins or so.. if she isn't gonna go back to sleep, you will know by then.
Get her up and keep a very close eye on her watching for tired signs - put her down as soon as you see some.
If she wouldn't go to sleep at 1 hr of A time, try 1 hr 10 mins (but not after a shorter than 90 min nap). If she has a nice nap, go ahead and push her A time to 1 hr 15...
I tried the 1 hr A time and she couldnt fall asleep for the next 40 min!
She was probably undertired and then became overtired by the time she did fall asleep...
How was her nap?