Evening, in Supernatural I have a human sim with the Lover of the Supernatural, but the other sim Vampiro, despite being the best friend, and knowing all the other traits, does not know that, why? The interaction no longer learns to know

It is (probably) an error in the game's programming - that trait cannot be learnt by other sims.
All traits have two settings called "CanBeLearnedRandomly" and "CanBeLearnedThroughConversation". For Supernatural Fan and Supernatural Sceptic, these settings are set to 'false', so the game does not allow it happen.
Probably a mistake on EA:s part - there's no logical reason why other sims should not be able to discover these traits.

thanks for the explanation, now I understood, it seemed strange indeed that it did not happen