broody advice

if the chick isn't feather or colour sexed you could have a male - what would you do with that?
It would also be best to get at least 2 if not more rather than just 1.
She may not accept it especially as she has been broody for 3 weeks - they normally start coming out of broodiness around 3-4 weeks.
Yes the others may attack it but the broody often will cover the chicks to protect them.
Yes you need chick crumb and if you buy one that is medicated then you need to stop the others that are laying from eating it.
I always had my broodies and chicks in a different coop but let them out with the others after a morning feed - this way they could mix with the other hens, then after a couple of hours popped them back in their own coop and run.