It is rare, but from time to time I observe inactive vampires turning their romantic interests into vampires. I went through my mods and didn't find any tuning mod that set this interaction to autonomous. Now, as turning other Sims is considered a romantic interaction I wonder whether it might actually be WooHooer that does this when romantic interactions are set to be autonomous for all in the settings.

Is this likely and is there a way that I can stop this?

And while I am at it, forgive me for bumping this one here.

That's autonomous by game default and it's not just romantic interests but also good and best friends since it's mainly a friendly interaction that can get the offer romantic interests just have a higher priority you can try to turn it off but from my experience it doesn't do much good if the game decides to push the issue which it sometimes has a tendency to do.

Hm, that's weird. I've never seen vampires drink from other Sims autonomously let alone turn them into vampires on their own until recently. I've been looking at SocialData_BaseGame and "Vampire Offer To Turn" is set to be neither autonomous nor as a friendly interaction. Unless I am looking in the wrong place or read the file wrongly.

I also checked Retuner in the meantime and there, too, it says, that Offer To Turn is not autonomous.

That's the game core that pushes those interactions whats in the Social Data doesn't matter too much. Although if you where to set those as Autonomous then you would seen it happen more frequently I have bluegenjutsu's Auto Vampires mod and I've seen happen more often with it than without and yeah I forgot it's a neutral interaction blue's mod has it set as friendly so my bad there. There are interactions even tho set to non-autonomous will fire off as they have a trigger in the game core but only fire off rarely.
And if it was woohooer making the interactions fire off then Retuner would've shown the interactions as autonomous or you would've seen something like Nraas Offer to turn when checking with Retuner.

I'm unable to find where woohooer would be doing this and I'm unaware of any mechanic in the core where it would be pushing and ignoring social data. There's a Ask to Turn too, is that one autonmous in your game? Any vampire scripting mods?

By game default Allow Autonomous and User Directed Only are both set to false for both Ask to Turn and Offer to Turn so it's based on the situation.
So it would have to be the game pushing under the right situational circumstances which could be controlled in one of the Occult Vampire XML's but I'm to sure on that.
But I do know it's the game that is pushing those 2 interactions there are several interactions where AA and UDO are both false but you still see those interactions pop up

No vampire script mods that I know of. I have a modded SocialData for the SN EP, but the interaction is not in there. Woohooer was so far my most likely suspect, because the drink interaction does have an effect on gender preference which made me believe that romance does figure in the turning bite, too. But I will keep digging further now.
So, did I understand this correctly Retuner would show any current tuning settings even if they are due to mods?

Yes if you have a tuning mod that changed those or any other interaction Retuner would see the changed value as tuning mods hard code the changes on load up.
Retuner sees what they are currently.