Hi Robyn,
Weighing her weekly is very important. How old is she? What size cage is she in now? What size is the wire on the cage?
I would definitely keep the two females separate until you are sure one way or the other. Sometimes a female will kill another female's kit/kits.
IF she is going to have kits there's allot to do in preparing for their arrival.
Using cardboard around the bottom of the cage is to help prevent the kit, should she have one, from climbing up the side of the cage.
Chinchilla kits are born with their eyes open and ready to play within hours.
Usually withing 24 to 48 hours of being born, they will even climb to to top of the cage.
They can climb up, but can NOT climb down.
So, when the kit gets to the top, it just turns loose and drops to the bottom of the cage.
If the cage is to tall (over 15") and there is not enough soft bedding in the bottom, the fall could kill the kit.
Keep us posted!
Jo Ann