She should (hopefully) not be far along at 11 months of age, mine normally come into heat for the first time between 8-12 months.
Most breeders introduce between 11-16 months or hold off until their pelvis is large enough. Once they get pregnant the pelvis quits growing making it very difficult for them to pass kits if it wasn't large enough to begin with. Chinchillas continue to grow and fill out until they are 3+ years old, they are very slow to mature.
I've never seen any proof behind the nipple thing though it is occasionally brought up at shows and meetings by new breeders. The most common method is manual palpation or watch for a mating plug (big long wax thing). Most big breeders just waits six months, douch/clean the uterus, waits another six months, maybe swap males, then cull.
When they are within three weeks of delivery you can hold your hand under her belly - mine gladly rest on my palm - and feel the full-contact football game going on inside. As she gets even closer you will see her sides visibly ripple.
This is a big time of year for having babies, the next wave is usually around March/April unless you've got lights on timers.
Good luck!