I need advice ASAP please...egg in nest hatched!

[Country Mouse]

My bantam hen has been sitting on an egg for about three weeks and lo and behold, the egg hatched (today, I think). It was just one egg and I never actually expected it to hatch but thought I'd let her give it a shot. She is in the rabbit hutch coop inside the chicken run with my bantam frizzle roo and noone else.
Am I right that I should get him out of there?
What else do I need to do? Should I leave the tiny little chick with her mother? As far as I know this hen has never raised any chicks. Should I set up an indoor brooder and take the chick away? Or should I put mother and chick indoors together? I could close them up in the hutch/coop, but shouldn't I clean it? I would like to give the chick the best chance for survival. I am in KY, temps are between 50 and 75 this time of year.
I am a complete newbie and need step-by-step-for-dummies instructions.

 

[JennsPeeps]

Keep an eye on her and see if she protects the chick(s?). Some roos are really good with chicks.

 

[Country Mouse]

She is very protective of the chick, she has not left the nest and really went after me when I moved her to see what was under there. I was so shocked to see a tiny, fuzzy baby.

 

[JennsPeeps]

Sounds like she's shaping up to be a good mom. I'd leave the chick in there (esp b/c it sounds like WWIII to get it away from her!)