I would try three to five days. When the chick goes back to the flock it will be on the bottom of the pecking order, and may be the peckee instead of the peckor...but that's what you want...for the others to not allow this behavior and 'stand up' a little for themselves. If you see it continues, take her out for longer, again. Some unusual behaviors have no cut and dry answer. You just have to try different things, and hope it works, if it doesn't you have to make another decision.
You say you have a large space, that is relative I think...chickens get bored too. Provide perches in the run for them, obstacles to climb around on and under,, things to explore and peck apart, a few pieces of corn on the cob can provide several hours of entertainment, a bucket full of fresh dirt to dig through...you get the idea?
You say you have a large space, that is relative I think...chickens get bored too. Provide perches in the run for them, obstacles to climb around on and under,, things to explore and peck apart, a few pieces of corn on the cob can provide several hours of entertainment, a bucket full of fresh dirt to dig through...you get the idea?