If she wants to leave him, and he doesn't want to break up his marriage, the word you are looking for is "no."
"No, I don't want a divorce. I can't keep you from leaving, but I won't make it easy on you. I don't believe in divorce. We promised to stay together through thick and thin, and this is just one of the thin times. It will get better. Whatever your problem is, we can work it out. Stick around, the best is yet to come."
I've never been married, so I don't really know how these things really work, but I am led to believe that your suggestion is one of those "works in theory" things...
One can say no until they are blue in the face. It is very easy to divorce someone against their will. One does not need to have or show grounds anymore in almost every state in country.
You must watch too many old movies. ;-) I think no-fault divorce is in all the states and has been for years, i.e., whoever files for divorce is going to get the divorce -- the only issues to be resolved are custody and property. With a good (there must be a better word here!) lawyer, the unwilling party can probably drag things out, but there's no such thing as contesting a divorce anymore. (There was a moving article in National Review a few months ago on this by a guy -- forget his name -- whose wife is divorcing him -- one of those "she wants to find herself" things; he's heartbroken, but there's no way to fight it.)
In this day and age, if one party wants a divorce there is very little the other party can do, legally, to prevent that. One can engage in a certain amount of foot-dragging--I did--but there is a limit; sooner or later the judge briskly orders the lawyers to move the case along and stop taking up the court's time. If the one who wants to leave really wants to leave, no amount of marriage counselling is going to work because s/he won't actively try and participate.
Sometimes "Just Say No" doesn't work, sad to report. I'm speaking from experience here.
LOL!
Divorce is now a "no fault" action in most or all states. That is, there doesn't need to be a showing of mistreatment; one party acting alone can obtain a divorce; consent of the other is not required.
So, is a person whose spouse divorces him/her guilty of abandoning the marriage? No.