She just started to bite, and she never did before. I've had her for about 3 weeks, and she is 3 months old. I am doing everything right, and I read all about chinchillas before I got her. So, if anyone can help me with this problem that would be great.

Does she always bite or just once and stops?

If its just once and stops she might never stop. Chinchillas do what's known as a test bite on just about everything to see if it's edible.

Also chinchillas are more grouchy during the day, so if your playing more during the day she is more likely to bit than if at night.

we had this problem with our chinchilla at first. he only would bite when we were trying to pick him up to bring to play. once we started letting him out more often and letting him jump into our hands instead of picking him up it helped like 90%. like the other person said though, if it is just little nips it might be a friendly gesture. if the bites are hard enough to see bite marks or bleed than it is most likely not friendly. chinchilla also do not like much change in their schedule. if you have started being louder during the day or maybe if you switched where the cage was, these could be causes of biting.