It does take a long time to get a new bird added, average time is about 3 weeks, but it can drag on for months. When you keep her separate, it drags it on indefinitely. If they're pecking through the wire, you can prevent that by lining it with hardware cloth at chicken height.
I've also caged the boss hen while letting the picked on one mingle, sometimes that helps (using a crate in the run). They all have their little personalities, so it can take several different tries to find the right approach for the group you have.
Being crowded complicates it to a whole other level. An outright refusal to mingle.
As always, it will take the birds some time to adjust to the new space. Chickens do take their time in adjusting to new things.