Disclaimer---I am not a mental health professional of any kind. I find psychology fascinating, and the following is my opinion, based upon what I have read and studied on my own.
Some mental illnesses or personality disorders are less evident when a person is younger, then become more severe in early adulthood. Some types of deviant personalities, such as sociopaths, are very proficient actors. They are aware that their true personality is not socially acceptable, so they observe "normal" people and imitate their behavior. They can be extremely deceptive.
When a "normal" person marries a sociopath, they will gradually experience more and more of that person's true personality...it is hard to accept the fact that the person you thought you married really fooled you into believing that their "public" personality; the one you saw before you married them, was not their true personality. When you live with someone day in and day out, they can't keep fooling you forever. If their true personality is sociopathic, and they become aware that they can no longer control you by fooling you, they decide to get rid of you. "Get rid of" can mean anything from leaving, divorcing, alienating your children from you, taking the children, leaving you penniless, up to or including physically harming you or murder. Just depends upon how sick your partic ular sociopath is!
Sociopaths live among us. They blend in. They can be charming, smart, successful in their chosen field. A young woman; even a very intelligent one, can be fooled in to falling in love. It happens too often!