It absolutely is a toxic way to think. So many things can happen over the course of a marriage. No one goes into a marriage thinking well this isn’t going to work. But tit happens. That old school mentality she has about how things should be will be her ultimate downfall.Clancy has a really bad attitude, she essentially doesn't believe in divorce I think she referenced she would sign a pre nup or entertain the idea of one because she doesn't believe in a marriage ending, or more so she wouldn't marry someone she doesn't see spending the rest of her life with.
I think it's a toxic way to think because anything can happen over the years, people change etc