G.M.
How long is she awake in the night?
Since she is basically sleeping 13 hrs at night, she is not able to sleep well during the day.
Most 12 mos olds sleep 13-14 hrs a day. She is doing most of it at night.
I would cut her sleep down at night to 12 hours, move her nap to 12:30 or 1:00.
Try this gradually over a few days and see if it helps!