What’s the problem with getting an annulment. No one in the Church thinks that suffering with a mentally ill spouse is something God wants for anyone.
I’m not sure what the law is. From what happened, I suspect a divorce is the legal instrument of the state and an annulment is an instrument of the church. It’s my understanding that afterword he got an annulment.
Well. you're right about that…but that's not what the law of the Church says.
Many, many annulments are given because the tribunal believes "suffering with [fill in the blank] is not what God wants for anyone", but, if each party was NOT mentally ill on the day of the wedding and if they both intended matrimony, and presuming the marriage was not illegal (age, consent, consummation, open to children), then, whether or not God wants the spouse of the now severely mentally ill [or whatever] person to suffer, that's what the law says he or she must do.