Is she a Silkie? They are made for this, used for hatching out eggs of even other species. We just did this, yesterday, with our Silkie who had never been a mom before.
She was great. My dd found a hatching chick on Monday morning, a little before we expected, and so she pulled the Silkie out of her nest box, and put her in a box with pinechips in the house. She let her get used to the idea by having her sit on some warm eggs for a short while. Then she slipped the chick under her wing, and the hen made happy momma sounds.
This was in the morning, in a box providing little light.
The rest of the eggs are hatching under her, but they had all come from other hens. She was just broody, and we weren't sure how long, so it was a test.
Even though she went through the upheaval of the move into the new nest, and it was her first time, there was no problem.
There can be though, so I would stick around to see how it goes. You might try the evening when it is dim and you are still up. She should sound happy, I know... you're thinking, "what's that?!".
When we had the Japanese who was not ready for chicks, she made a different disturbed sound. Even she did not hurt the chicks, but just jumped out of the box. My dd spent the night in the room with them, so she was able to hear the chicks peeping when the hen left.
Hope it goes smoothly for you.