My daughter only sleeps for an hour and 20 minutes each nap time and usually wakes upset and cranky. She clearly needs more sleep as when she sleeps two hours or more (which is rare) she wakes really happy. Any advice on why she could be waking so early if still tired? I usually put her down five and a half hours from waking in the morning, so usually a 7am wake up and 12:30pm nap.
You might find she is cranky because of the stage of sleep she is in when she wakes, i.e. she wakes up when she is still in deep sleep.
It is very common for children at her age to wake up cranky and it is not necessarily a sign that they have not slept for long enough.
I would suggest that you extend her first awake window to closer to six hours and pop her down for 1pm (ish).
You might find with a slightly longer window she sleeps for a bit longer.