Hen on roost with feathers fluffed

[Kestap]

My 7 month old Easter Egger, Jami Hendrix, is acting strange. BTW - these are my 1st chickens. She is sitting on her roost all fluffed up and will not go outside. The other 3 go in and out all day. She is not spending the time in the nesting box all day and is splitting the rest of the time perched on her roost. She is eating and drinking and looks great but her behavior is concerning. The outside temps have been in the teens and now in the 40s but they have the coop heated at night (around 45). Should I be concerned?

 

[Den in Penn]

It might be she is feeling off. If she isn't wheezing or runny poop and she is still eating and drinking I'd just keep an eye on her for while. Or it maybe that she is in the first stages of going broody and not ready to set just yet.