I had the same crash, but looking at the files I figured out why.
the "é" of fiancé seems to use the wrong encoding. In fact multiple .d files of the Petsy mod seems to use a different encoding than the main game. Here is how I realized.
From the Petsy mod:
188043:That's why we are a marvelous couple, my fianc�!
One from vanilla game:
96576:My contact, Sanik, is dead; I must go to Lady Galvena's Festhall to speak to his fiancée, Claire, to see if she knows anything about what Sanik was about to tell me. There may be another way into the asylum, but without Sanik's help, I don't know what it might be.
Edit, maybe that's not the bug. The following lovetalk also sometimes crash my game depeding on the choices I make.
There is also another annoying bug that doesn't crash the game: Petsy's dialog with Sam Thunderburp in the Five Flagons loop.
Same by the way with Skie and Garrick in the Temple district (I noticed you're the author of that).