Stray hen joined foraging flock

[SlyReb]

Yes I know the quarantine procedure so I don’t need that lecture here.
I initially chased her off but my hens forage all day on 4 acres. This hen wandered into the yard and joined my flock as they foraged before I was aware.
She is young and appears healthy. I have asked all the neighbors I know who have chickens and they are not missing one. But it’s a rural area so I can’t be sure.
My three hens are fine with her tagging along to forage, but they do not want her in the coop and chase her out. When they are in the coop she sits outside next to it. There’s only a screen between them.
I assume she is roosting in the woods at night. I also think she is laying in the woods as I’ve seen her march purposely off around noon each day.
She won’t let me near her and I haven’t tried to bait her as I’m not sure what I want to do.
Any suggestions beyond what I’ve already done?

 

[3KillerBs]

Maybe the hens will decide to let her into the coop one night after they get used to her?

 

[McChooky]

Some people just dump their chickens off in parks and rural areas when they can't keep them anymore. Hopefully your flock will accept her and allow her to stay in the coop with them soon. I don't imagine she'll last long if she continues to roost alone outside a coop.