I’d never let it get to that point in the first place. Get those things out of the way up front, before there develops such an attachment, that it would be hurtful and even traumatic to both parties, to have to break the relationship.
Better not discuss it beyond that. I have found (even on this forum) that some Catholics are scandalized by one who is in a marriage bond — as I am — even
hypothetically entertaining the possibility of marrying someone else, and entertaining this thought while either their spouse is still living, or while they do not have a declaration of nullity yet.
(The latter was on my short list of things to pursue in 2020, but then came up COVID-19, grave illness in my own family not connected to CV and expanded caretaker duties, and the need to create a concentrated homeschool curriculum for my son. I’m too much of an ornery old cuss, set in my ways, to be thinking about marriage anyway — she’d probably end up putting cyanide in my iced tea,
and not without some justification! )