
Talking to Brennus the same turn I destroyed Elizabeth, so he no longer has a worst enemy.
Like SOTD4, this is another diplomacy text error: if a leader has a "worst enemy" (someone they dislike the most) and they are killed that turn, then the diplomacy text results in this message. Apparently, the game doesn't update the worst enemy data during the turn.

The turn I defeated Lincoln I was going to go vassal Catherine and this came up and I could not bring myself to not screenshot this

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