A bit more background on DID. I am by no means an expert on DID, so that’s why I’m pointing you to these resources, but I do know a fair deal about SZ/SZA and have experience with ‘voices’.
What you are describing in your wife sounds similar to what DID people call co-consciousness which means multiple alters being aware of each other and events. To be classified as having DID there needs to be a degree of amnesia between alters. More typically, a single alter will have control of consciousness at a time and the alters will have little to no knowledge of each other. As with SZ, people with DID can become adept at coping/covering their symptoms to a certain point, but there can be a tipping-point where things spill-over and they are noticed. My understanding is getting to a point of co-consciousness normally happens during therapy, but I suppose it could happen spontaneously.
Here are a couple videos by people diagnosed with DID speaking about the differences between DID and SZ. Be aware that DID and SZ can be comorbid (happening at the same time). DID generally happens in childhood, but may go unnoticed until much later, while SZ generally develops in early adulthood.
Here’s a link to a thread with DID forum links at the end: