Loving wife and mother

BKW

I am the husband of a wonderful woman to whom I've been married to for 19 years next week. I'm not perfect but I thought that we had almost the perfect marriage. 4 months before my wife found out that she had breast cancer, she surprised us all with she wanted a divorce( me, mother, father, sister, the whole family) my question is was my wife's body possible going threw changes that she wasn't aware of that made her act this way. My wife never believed in divorce, hurting our children or me.. Her co worker for the last five years said that she bragged on me daily about what kind of husband I was and father I was. And no there is not another man. But I'm wondering did any woman out there have these sudden changes of anything like this before they found out they had breast cancer. Please help me understand what she might have went threw and maybe help her understand that it happened to others. I need my wife back, I want to be by her side to kick cancers butt. Thank you