Wanting a flock for solo lady

[Manupprincess]

We got 5 former battery chickens to start with. Unfortunately two died pretty soon afterwards (they were in quite a poor condition) and two were killed by a dog with a very indifferent owner
Our remaining lady has been with us for a few months but as they are naturally flock creatures I want to get her a few companions. She is doing really well but it just seems a bit mean for her to be on her own.
We're looking to get three rescue chickens but I'm looking for advice as to how we can successfully introduce her. I was told it's best to clean the coop out with vinegar (gets rid of the smell) and to do it at night but not sure if this is true. Any other advice?
Oh and no way any dogs can get in now unless they are actually put into the coop.

I was down to one lone hen earlier this year. Ex battery too. I just bought a few new hens and put them in together. Cleaned out the coop (normal weekly emptying of bedding.

They were fine within a couple of hours. My hens have got lots of room so I didn't wait until evening which I might have done if they were in a run. I have heard the introducing them at night thing before but never done it.

Thanks, that's reassuring. We're going to wait until the new year when hopefully the bird flu issue has eased and we can give them a much larger run.

The recommendation when introducing any new birds is a 2 week quarantine period for the newbies in a fully separate area, followed by 2/3 weeks in an area next to but separate from the original bird(s). By this point, an integration should be fairly smooth but worth doing it when everyone is free ranging again so any picked on birds have space to get away.