I think the chewing is quite normal for a preggy hamster. Our hamster nibbled on the wires of her cage prior to her birthing. Giving her something to chew temporarily stopped her act. We have a teddy bear hamster.
Good luck on taking care of them! Just be observant on what she does. Try covering her tank too to isolate her so she'd feel more safe. I did just that when our hamster gave birth and all the little jellybeans survived. ^_^