little spoiler alert.
I don't believe she has any intentional involvement in the werewolf's infection and was just a slut at first but maybe she is also now a pawn of the person who is taking them? also, the mystery person doesn't have the ability to give commands to all the werewolves just the one he has under his control, the one that runs to him in our latest Logan event. however, I do believe he can control the swamp creatures due to the giant one that shows up, and maybe was planning to get ALL the werewolves that night using the big guy.
(And what we currently know about Serena is literally only that she went kinda insane from getting fucked so good by beasts that she is just sitting in the werewolf cave getting fucked to this day. kinda like the MC bad ends but this one we see the aftereffects of what happened instead of having to reload a save. also, that she was unhappy in the marriage because she suddenly wanted a LOT more sex than Logan was able to provide. maybe the curse of lust somehow affected her as well since we know she went into the forest before she was having marital issues and might have drifted a little close to the corrupted swamp zone?)