HELP I need some advice about my chicken

I have has her about 18 months and she was broody about a month ago and is now molting but that is not the problem I introduced 3 new girls 3 weeks ago and every thing was fine for the first 2 weeks but for the last week she has taken to going to roost on top of the coop rather than inside, while I don't have an issue with this I am concerned that the local fox or a passing cat might get her, also it has been very cold and wet over night and as she hasn't got all of her feathers I am concerned that she might catch a cold.
I am trying to creep up on her and put her back inside but it is getting harder and harder to catch her.
So has any one any ideas how I can encourage her back inside over night.
Thanks
Karen and a very cold wet chicken

Sounds like she is being bullied by the others. Can you give her her own pad? Perhaps a space in youtpr garden shed or garage. A cardboard box with the sides cut down and some straw - otherwise it is going to be your kitchen. Shut her in it. If you are having problems catching her then you will have to net her to get her in the box.

Definitely sounds like she's being bullied by the new ones.
They were probably just feeling nervous in a new place at first, hence no problems till now,but now they've had time to settle, find their feet & have started throwing their weight around. They'll have an established hierarchy amongst themselves, pecking order, but she is something new to them.
If you catch her & force her in with them she'll become more & more frightened & they could end up seriously hurting her. Not the most kindly souls chickens.
You do need to separate her from them. If you can put her in a run next to them during the day, where they can see her but not touch her, they might come to accept her in time but I wouldn't bank on it,

Thanks for your advice, she has gone in with them all for the last couple of nights so I am hopeful that they have sorted them selves out. there is plenty of space both in and out of the coop for her to get away from the others so I am going to keep an eye on her and make sure that she is getting plenty of food and water by having several feeders around and spreading out the corn over a wide area.
If it doesn't work out I really do not know what I am going to do as there is nowhere else to keep her. the chickens have the front garden and my 3 dogs have the back, It really wouldn't work trying to keep hr in the back garden with the dogs, while they might not deliberately hurt her they would want to "play" with her and I couldn't guarantee her safety with them and I have always read that chickens need to be kept with other chickens to be happy which was why I brought the new girls to keep them company.