That’s a hard call. I let my hens hatch with the flock and raise the chicks with the flock, but you are in a different situation. Your Mom doesn’t have a rooster, I think a rooster often helps with young chicks in the flock. For whatever reasons it sounds like the Silkie has not truly joined the flock. At one year old and with that shake-up to the flock pecking order that’s kind of unusual, but it is what it is.
In your case I would suggest you isolate her before you give her the chicks. Make sure your fencing has tight enough mesh so the chicks can’t get through. Make sure the area is predator proof for nighttime, that’s where your greatest predator danger will be. Then, after a week or so, I’d turn them loose to roam. By that time the other hens should have accepted the new additions and not go out of their way to harm them. But let them loose when you can observe. My hens usually don’t bother the chicks anyway, my broody hens protect their chicks from any threat from other chickens (usually juveniles but possibly from an adult hen), but you never know how living animals will behave.
If at all possible, build that isolation pen in the coop. That should be predator proof and will keep the hen and chicks with the others. But after keeping the hen and chicks in that isolation pen for a week, the hen will almost certainly take her chicks back there to spend the night. If that is not in the main coop you will have to transition them at some point.
They should be able to share a coop, just try to not leave them locked in there together late in the morning for the first few days. I do that when I integrate young chickens, make sure I’m down there early until I’m confident it won’t be a problem. It’s never been a problem, usually two days is enough to convince me it won’t be, but you can never tell with behaviors.
I don’t know how the flock dynamics will work out when those chicks mature. You may wind up with roosters. What I’d expect is that the chicks will form a sub-flock and avoid the older hens until they mature enough to force their way into the pecking order. With cockerels, who knows when that will be? With pullets it’s usually when they start to lay. When the Silkie weans her chicks they may form three flocks until they mature. They may stay with the Silkie even after they are weaned. If they join the main flock when they mature they may take that Silkie with them. You just don’t know what will happen with chicken behaviors. But I think it is worth trying.
