1. It's not necessary, but if there's some way to give the new hen home court advantage by living alone in her new place for a day or two that's good. She'll feel a little more confident and will view your old hens as the "new" hens and that will give her more confidence if your old hens don't take a shine to her right away. The new hen won't actually feel like the new hen.
2. It's not necessary, but if there's some way to give the new hen a chance to get a feel for the new place without the other hens around, that's helpful, too. You know, so that she knows where the water is and the feed is and is a little bit used to it before she meets the other hens, then it's easier for her to get a chance to eat over the next few days if your hens end up being a little territorial with the food and water. Plus knowing where the roost is for bed time.
3. They will almost assuredly be done figuring out their pecking order by Thanksgiving. The adjustment usually takes anywhere from just a few hours to two days. Usually.
There are so many, many variables that it's really difficult to figure out what will happen. It's usually pretty difficult for me to watch, but many times it amounts to nothing but a few swift pecks and a little rudeness and snotty attitude from the original hens. Hens don't understand hospitality.
If nothing else, if you put the new chicken in at night, then at least they can get slightly familiar with each others' noises for a few hours before they really get to working out the pecking order.
I'm thinking your friend's chicken is already over 5 months old and that yours are, too.
Chicks would take another little pen for you to raise them in ... depending on how you want to merge flocks. I think it would be more difficult to get chicks right now with colder temperatures coming in for a good portion of those living in the northern hemisphere. But I don't know exactly what you need or your long-term goals.
