Check these two hubs out:
Have you sprayed anything in the room? Any kind of spray or aerosol can kill a chinchilla, as they have VERY sensitive respiratory systems.
What are you feeding her? Make sure that it's a sole pellet diet with no dried fruits or whatnot in the food. Those should be treats and treats alone that should not be more than 10% of the diet. Also make sure that you're providing plenty of timothy hay as well.
If your chinchilla is showing signs of illness, you need to seek medical assistance, as they generally do not show signs of weakness unless they are feeling extremely bad, and generally at the last minute.