Ok, well. Just for future reference, you should always quarantine new chins for at least 4 weeks. This means having them in a seperate room and washing every time you go from chin to chin. This prevents the spreading of any illness that either chin might have.
However, it's a little late for that now so here goes...
Generally, females go into heat about every 28-35 days. "Breeding season" usually starts around the end of October into late spring (around May) but females can give birth between June and September as well.

Females will also go into heat immediately after giving birth and once the kits are about 5 weeks (once she starts weaning them).
As for pregnancy, there are several ways to tell if a chin is pregnant. The gestation period is about 111 days. The female will really only start to put on a lot of weight in the last half of the pregnancy...that IMHO is the best way to tell that they are pregnant. Start weighing her weekly and keep track of the weight. She will start eating, drinking and sleeping more. She also may get irritable at which point, you may need to remove her mate for his safety. In preparation for the birth, make sure that you have a baby safe cage. The wire spacing should be no more than 1/2"X1/2". You will also need an extra cage for Chilly because he will need to be removed shortly before the birth (or immediately after) to prevent him from mating with Genie again. This is called breedback.
Here are several links on breeding. I barely scratched the surface.
http://www.twitch-chinchillas.com/breeding.html http://www.geocities.com/Petsburgh/5...nbreeding.html
Here is a gestation calendar so that you have an idea when she is due.
http://chinchilla-exchange.hypermart.net/Gestation.html
Feel free to ask as many questions as you like. There are many experienced breeders here that are willing to help.
