You have a medical condition
Xarpolis
? I never would have guessed that when I met you, you seemed the picture of health.
Regardless of the stuff you posted about her family, I'd say that
@Control is pretty on the money here. Japanese women are conditioned to treat their husband as the breadwinner and that culture is a hard thing to break. She never had any problems with you when you were employed with a good job right?
I hate to say it, but Japanese women tend to look at marriage as a business transaction rather than a love thing. They pick a guy with a stable job and income and settle in to become a mother by 30, at which time they will quit their job and settle into being a homebody. Have you ever talked to her about her future plans? She's a nurse, but does she want to stay a nurse or does she want to become a full time mum?
A Japanese woman wanting a divorce is like.. ridiculously rare. Divorces in general are very, very low in Japan (probably because of that marrying as a partnership thing rather than for love - as long as your guy is still providing or your woman is still taking care of the kids, all is right) - a lot of my students can't stand their wife, and this is a big part of why Japanese men work so much.
Sooo, the fact that she brought this up point blank. I'm frankly shocked. I have to imagine it's pregnancy hormones and your lack of job related. My advice? Talk to her parents. They can probably give you a bead on what's going on.. and it may be a bit underhanded but they will probably put a word into her ear not to do it. No Japanese parents wants their pregnant mother of soon to be two to be thinking they want a divorce.