There are several options when one of a pair passes, but it all comes down to the individual chin and how sudden the death is. If for example if one is doing poorly and needs to be put down you can introduce a cuddle buddy stuffed animal to them so the toy smells like it's cage mate before she passes. You can also try introducing a new chin to the current one if you want. Once again depending on if the cage mate died suddenly or not you could get a new chin before the other passes to start a new bond before.
The biggest thing to remember though is your chin will probably be grieving just as much if not more they you are, so make sure you spend extra time with her. Chins can suffer from depression and in some cases do need a vet check up and sometimes drugs (mood drugs, appetite stimulants of they aren't eating, etc) to get over it.
