you can take them from her, though you should probably wait a couple of days to handle them. one of my broody silkies raised a few chicks, and we were able to pick them up just fine, though it depends on the breed of hen going broody. Some are meaner than others when broody.
Hope this was...
The momma hen does need to look after her 2 chicks, and it is completely ok for chics to be on their own, as long as they have 1 or more chicks with them. I've raised chickens straight from the brooder without needing a hen, though the new mama probably won't take the chicks back, as she would...
I think that each hen starts laying in their own time, and that the farmer guessimated how old they were, so you never know, the hens might have been hatched on different days. Also how long have you had the hens? If you've had them for 2 weeks or under,she may still have a little time untill...