Does she seem sick or is the long time the only problem?
My hens take varying times to lay, with a few sitting for no more than 20 minutes while others have taken an hour. I think it's up to the hen, and if there's no other signs of sickness I wouldn't be concerned. As long as the eggs and behavior of the hen are normal and healthy, she could just enjoy taking her time.
However, I'm no expert on diseases and problems. I had one egg bound hen who died because I didn't notice the warning signs early enough--but sitting for too long on the nest was not a symptom. I don't think she's egg bound if her feces and eggs continue passing regularly and come out normally.