Do the thumb test on her first. Lift her tail and place you thumb just under it. You will feel a hollow that should be just big enough for your thumb to rest in it comfortably.
This means her pelvis is delveoped enough to born kits.
If you can't she is too young to breed and I would wait a few months.
Do remember ... everyones thumb is a different size ... this "scale or measurement" is based on the
average man's thumb ... if you have small hands, it is not as true a measurement. And you will need to make allowances.
Is it too risky to put them together within the month?
Without knowing more, I would not, but that's my personal opinion.
(I'm not TRYING to breed them. I mostly just wanted Dewey to have a mate because he was lonely and didn't go for a male friend. If they do breed, it's fine though).
Anytime you put a male and female together, you the take the chance/possibility of producing kits, if they are both fertile..
How likely do you think they are to try to breed immediately?
Will they try? He probably will ... it's in his nature. Will it be successful? Depends on both of the chinchillas.
(1) If she is or is not in season at this time.
(2) If both are fertile.
(3) If they both remain agreeable, after being put in the same cage ...
I've had ones that have connected the first day and some a few weeks/months later ... one pair did not produce a kit until 7 years after being put together ... and that was the only kit they had ... they have now been together over 10 years.
You might want to think about getting a proper whelping cage before putting them together ... with a litter of only one kit ... sometimes, it is hard to tell she is even pregnant.
The 500 + grahams is almost a must for the female ... for it to be safe pregnancy for her.
As a rule, it is best if the female is larger than the male ... for the odds to be in her favor, for a safer delivery.
But ... it's your chinchillas and you must decide ... we can only give you advice, according to our years of experience.
Jo Ann
BTW They are adorable in that picture!