// I cornered her today and after a lot of struggling I held her down//
Do you realise how much stress that would cause a hen?
Your attitude it typical of a Vegan. Animals have to be treated like animals not humans. You have introduced one hen into an already established coop and that will always cause problems. Hens have a very clear heirachy in the flock -some will be dominant and some submissive and there is nothing you can do about it.
Three things you can do:
Let them get on with it and hope they sort themselves out
Take away the bantam and put her on her own -she will not be happy on her own.
Buy another bird, put it in a seperate place with the bantam until they get used to one another, then introduce them both together back into your flock.
Why are you buying hens as pets if you are Vegan? What will you do with their eggs?