chicken sleeping habit

We recently introduced a new chicken to the pair that we already had. There has been the usual pecking order kefuffles, but nothing serious, and she's been hanging around them more and more without incident, the new chicken has found that perching on the top of the coop is her safe space. She has also decided that she wants to sleep on the top of the coop rather than inside the coop with the other two chickens. We've been going out at night and putting her inside the coop, hoping that she would get the idea and go in on her own, but no luck so far. The coop is in a predator proofed enclosure, so there's no fear of anything getting to her, and the night time temps range from 30's-40's. Is it okay to let her stay out on top of the coop at night? Thank you for any advice!

What will she do when there is a storm? How big is your coop and how much roost space is available? Even if they are getting along pretty well there can still be fights over roost space at bedtime and the low bird on the pecking order will be reluctant to try to roost if she's getting bullied or even just getting threatening looks from the others.

The coop is not very big (even though it is advertised as being big enough for 4 chickens) and there is only one roost which is big enough for two of the chickens. When we look inside at night (before we put the new chicken in), there's always a different sleeping combinations - one chicken will be on the roost and the other chicken is in the nesting box or just on the floor of the coop. Or they're both on the floor of the coop and no one is on the roost. There are two nesting boxes, and sometimes we'll find one or both of them sleeping in the boxes; there doesn't seem to be any consistency to where they sleep.

The coop is in an enclosure that has a covered roof and plastic sheeting partway down the sides, so it stays pretty dry when it rains. However, it would still be nice if she were in a sheltered coop. We can try to add another roost inside, but it will be pretty tight. I think your point about her being reluctant to force her way into a small coop is probably right. They're getting along better and better, but I wonder how long it will take till she's comfortable going in on her own? Thanks for your help!

Welcome to BYC!

Coop and roost is probably not big enough...especially with a newly introduced bird.
You really don't want them sleeping in the nests...will make for poopy eggs when the time comes.

How old are the birds?

What is your climate?
Putting your location in your profile can helps folks give better advice/answers.

Pics of coop and run, inside and out, might help us help you find a solution.