I would like to think yandere fairy would have a slightly similar vibe to Silas since elves are kinda like a sub-spicies that evolved from fairies but would also be fundementally different.
Like elves are more detached from fairies thus require spells and grimoires to actually use magic, meanwhile fairies are naturally magic and can cast it as easily as breathing.
I'd also like to think fairies would be more likely to commit evil without fully grasping the situation. Elves are more rational and stoic, they usually have no interest in others and only care about their studies.
But fairies would carry a lot of strong emotions in their tiny bodies. They'd express their love more freely, they'd get angry or sad easily, they'd have a lot more energy to them.
If a fairy falls in love with you he'd try to appeal to you by gifting you flowers and fruits, and at first you'd think that he's oh so adorable. He'd hide in your hair, give a shy little kiss to your cheek, hug your finger with his tiny body begging you not to go.
Alas a fairy's love is very deep, obviously he'd go above and beyond for his soulmate. If the fairy sees someone being mean to you or putting you in a difficult situation he'd do everything in his power to help you. That's why the next time you go to visit your little fairy friend you'd find that person who has been making your life difficult completely absorbed into a tree.
They are still alive but they are silent and unmoving. Nature has taken a hold of them and as they are now one with the tree you can no longer separate them.
The fairy would be so excited showing it to you, flying around you like a pretty butterfly and pulling at your clothes, urging you to take a closer look at his gift. Are you happy? Do you like him even more now? Why do you seem upset...? Didn't he do something good for you?
He doesn't really get it. His little magical mind doesn't get the moral compass of humans, but that's okay. It's not that important. You two can just have some sweets and forget all about it. It wasn't that important anyway.
Ignore the rumors about having fairy food making you unable to leave the forest. He worked so hard to make something delicious for you with his tiny body. Look at how much he loves you.
