Is she a lone chicken or do you have others? If the latter, then there is something going on with your coop that she does not like. It could be a number of things, but better if you can provide further info, and maybe a pic of your coop.
Well, maybe she's just a bit of an oddball? Its both a strange location and time to lay eggs, but i guess she just feels safe and comfortable there?
Maybe she just wants to be as close to the humans as she can. I have one that I have to put up every night or she trys to sleep in the bush next to my bedroom window. She'll lay her head against the window and stare at me...kind of a creeper. ;)
She also trys to come in the house to lay eggs. She's laid them on our aussie a few times. He's 19 though and doesn't do much, I could see how he could be mistaken as a rather warm and fuzzy nest.