When someone changes so dramatically in a short time, there is often a medical explanation. I therefore suggest that the first step is a complete medical exam. It’s important to rule that out before concluding that there is a psychological problem.
If she is medically okay, it’s possible that she is depressed. Depression doesn’t always show itself as sadness. Sometimes it is expressed with irritability and anger. Since most people assume that depression is about a “depressed” mood, meaning sadness and apathy, they don’t recognize that anger and irritability are symptoms that need to be addressed. Further, managing the anger and the negative thoughts that come with it is exhausting so the person may have little energy for managing the tasks of daily life.
A risk factor for depression is perfectionism. The person is constantly measuring herself (or himself) to an impossible standard. Sometimes that relentless negative self-evaluation is projected onto others. One way for your wife to feel better about herself may be to at least feel better than other people — like the people in your family. This constant self-criticism combined with depression is also exhausting.
I have a guess that your wife’s apparent tantrum about finally getting married had to do with her age. You are both in your mid 30s and had been promised to each other for 15 years. If she wants children, her biological clock was ticking. That realization may have triggered frustration with waiting to the point where she could no longer manage it. It may be that blaming others and withdrawing are her way to cope with overwhelming emotional pain.
The way to deal with this is to stop arguing and to get your wife adequately and professionally assessed.
As I said, the place to start is with her physician. But if she is fine medically, then do make an appointment with a qualified psychologist to determine if the problem is depression.
I wish you well.