She is a blue copper marans. About 2 years old. Generally very sweet and friendly. Has been very diligent about sitting on her eggs. Poor thing.
I would try it and watch.
I have had 4 Marans or Marans cross (2 BCM, 1 Splash Marans, 1 Isbar/Marans OE).
Apparently this line (all from the same breeder) got the broody genes as they have all gone broody, stubbornly so, throughout the seasons.
Splash momma sat and hatched a chick (I only set 2 under her as she was a new momma). She did well the first week, but then abandoned baby and went to a high roost where baby couldn't follow. (She actually was trying to do that on day 2 or 3).
My other Isbar/Marans had sat for 3 weeks, got a hatchling, but it was apparently crushed by others wanting to crowd the box (I've been attempting to coop hatch again within the flock in an experiment to improve integration).
She was still stubbornly wanting to sit, so I took that 1 week old chick and put it under her, at night, from the back. She immediately clucked to it, literally took it under her wing, and has fully adopted it. (Splash momma has been happy with the adoption).
I am in working small batches as I've got new broodies and trying a new set up in the main coop, but I've over the years done really well with first time broodies. If it is in their blood, they do well.
All to say overall my Marans breed has been good brooders, and your Blue Copper Marans likely will be just fine with the babies...place at night as suggested, from the back, and then monitor for the next several hours, and check first thing in the morning.
Likely momma will be fine but babies may be confused as they don't know the hen is their heat and comfort source and that it should be dark all the time (vs. the heat lamp). Standing by is to help babies know to stay with momma as much as to make sure momma is accepting. I usually give momma some room to move, eat/drink, but confine things so foster babies can't wander away too far for the first couple of days as they need to learn to obey her voice....as long as momma is handling the brood well.
LofMc