I am speaking from experience when I say an electric fence is still worth it and you can get the electric netting and a box for less than $100.
How old are the chicks? They will be old enough to integrate with your hen by six weeks. I’ve put five six week old chicks in with my flock of fourteen without issues. I kept the chicks in a small coop and run that was inside the main coop and run so the big chickens can get used to them. They were in there from four weeks to six weeks of age and I put them with the big birds at six weeks. This would be easier than finding and quarantining a new hen.