One flock of 4 seventeen week old girls of mixed breeds....or a flock of seven bantam 4 week old silkies? the newcomer is a questionable age RIR hen. of course they won't be brought together till after a period to be sure of her health. What do you think? If she's broody, do you think she'll take to the chicks better? If she's laying do you think the big girls (who aren't laying yet)will give her grief? Do you think the big girls would gang up on her? Do you think she'd attack the 4 week olds?