Big Bird sleeping outside

This may sound normal to all of you, however, I'm new to this and am curious about one of my chickens. These gals are at 9 weeks now, they've been in the coop for 3.5 weeks. I started them in the top part with the run closed off for about a week or two until I gave them access to downstairs, which is closed in with hardware cloth. Well here lays the question. One of my birds, Big Bird, has been downstairs away from the rest of the flock in the mornings. Its still dark outside, everyone else is sleeping and she's just sitting in the corner by herself. She is not one that has been hanging out outside, in fact, besides the last two mornings, I've only seen her outside 2 times. She tends to hang out upstairs in the coop the most. She is a Cornish X, which i found out about two weeks ago and unfortunately will have to butcher her very soon. Is this a lazy behavior? Is her heart failing already? Help please? Thanks!

 

She was in a random batch of birds we got, she is twice the size of everyone else. We weren't expecting a meat bird. Everything I read said these breeds need to be butchered they are bred to grow really big really fast for production and their hearts cant keep up with the growth, so they butcher them at 6-8 weeks and otherwise will die of heart attacks sooner than later. I dont think she's too low on the pecking order. The other birds in the flock seem to be very sweet and nice to her. I think she slept out there last night. It just seems really strange to me after she's been in there for so long and hadn't come down. Do Chickens seperate themselves if they know they are sick like cats and dogs try to?

 

I originally thought maybe she couldnt get back up, but yesterday morning she was down, and by the time i got home from work she was back up. Then again this morning she was down again, I'll have to see if she goes back up. Maybe she just likes to sleep under the stars? But that just seems so weird to want to sleep in the wet dewy grass