If she was part of the flock before, it won't be too hard to re-introduce her. If you can confine her in a cage and put her in the area where the flock hangs out, you can watch the reactions. I have taken a hen and put her on the roost in the coop after dark so they all wake up in the morning together and she was fine. Other than a few squabbles to realign the pecking order, it was pretty uneventful.
Usually
not the case.
A bird removed from the flock can become a 'stranger' in just a few days.
Your technique described may work, but be ready if it doesn't.
It would be better to introduce one or two birds to her. There will be scuffles, but it should settle pretty quickly, then once they are pretty established introduce the pair or trio to the flock.
This is a good idea.
I think it's best to have a separate area adjacent to the coop/run to house to start the re-integration process and follow the.....
Integration Basics:
It's all about territory and resources(space/food/water).
Existing birds will almost always attack new ones to defend their resources.
Understanding chicken behaviors is essential to integrating new birds into your flock.
Confine new birds within sight but physically segregated from older/existing birds for several weeks, so they can see and get used to each other but not physically interact.
In adjacent runs, spread scratch grains along the dividing mesh, best if mesh is just big enough for birds to stick their head thru, so they get used to eating together.
The more space, the better. Birds will peck to establish dominance, the pecked bird needs space to get away. As long as there's no copious blood drawn and/or new bird is not trapped/pinned down and beaten unmercilessly, let them work it out. Every time you interfere or remove new birds, they'll have to start the pecking order thing all over again.
Multiple feed/water stations. Dominance issues are most often carried out over sustenance, more stations lessens the frequency of that issue.
Places for the new birds to hide 'out of line of sight'(but not a dead end trap) and/or up and away from any bully birds. Roosts, pallets or boards leaned up against walls or up on concrete blocks, old chairs tables, branches, logs, stumps out in the run can
really help. Lots of diversion and places to 'hide' instead of bare wide open run.
@Helicopter Mom in the future consider treating bird right in coop in a crate fitted out like this:
https://www.backyardchickens.com/ar...rates-a-good-tool-for-every-chickeneer.72619/
