I did some tests and got a villager to negative 5 hearts, and I got the message that they ended their marriage with me. The ring in their relationship menu showed they weren't married, but the nametag still said "Wife", and any interaction resulted in a message as if she were my wife.

I am using:

Forge 1.12.2-14.23.0.2491
MCA-1.12.x-5.3.1-universal
RadixCore-1.12.x-2.2.1-universal

I have no other mods installed.

Still having that pink villagers glitch, don't know if it's related

I did some more tests, and it seems divorcing via a Cleric doesn't properly end the marriage either.