Coconut should not have a nest box at 10 weeks old. Sleeping under the food dish on the floor of her cage is just fine for now.
She'll stop sleeping on the floor of her cage as she gets older and will learn to perch on the swing without falling off it as well.
Some budgies sleep in their food dishes when they are babies and/or try to squeeze themselves into tight places because it makes them feel more secure. These behaviors are quite normal for young birds.