First: sorry if my English slips sometimes. This is a long story so please bear with me. I will call her M and him B. The story is told in first person POV and M is the narrator. So M decided to befriend B, a two thousand + year old vampire who has, just a few months before, tried to kill her and her friends. He (obviously) lost and was gone for about a month before coming back and asking to be friends. M refused at first, but she eventually agreed to the friendship because she wanted to find out why he was targeting her and her friends, what he wanted with or from them, and why he had a sudden change o heart and wanted her friendship. She was always portrayed as more of an anti hero protagonist. However, after her best friend's cruel death before her very eyes, she's finally had enough and becomes a full blown villain. She calls her new friend, B, and asks him to mentor her to become a serial killer (she wants to kill the people she deems worthy of death because her friend died innocent and she believes that by doing this she's protecting other innocents), and he happily obliges. Now she's leading a double life: a serial killer by night, an agent supposed to deal with supernatural threats (yes, including serial killers just like herself) by day. She has a boyfriend who knows nothing of it. In fact, the only two people that know about that "friendship" thing are M and B. While M wants to get close to him in hopes of getting all those answers, B needs her because he is targeted by a woman he wronged back when he was still human (a very old vampire) and believes that M and her powers could provide him protection against that woman. It's pretty obvious to the both of them that they are using each other. However, M is starting to develop feelings for B. That wouldn't be a problem if not for the fact that he's basically the reason for everything bad that's happened to her (tried to kill her and her friends, kidnapped her boyfriend and tortured him, raped and murdered her ancestor who then possessed her to get revenge, attempted to kill said ancestor who was occupying M's body and thus almost killing her, attempting to rape her, etc.), and some of the things she doesn't even know about. None of those feelings weren't supposed to happen. As I was planning, and eventually starting to write it, it was supposed to be just a fake friendship with constant bickering and lots of pretend feelings. But since I'm writing through M's POV, I'm starting to realize that she's falling for him and now I don't know what to do. She suddenly trusts him and feels comfortable being around him, when just a couple months ago she would be more than happy to drive a stake through his heart. And yes, she knows that it's wrong to have those feelings and constantly reminds herself of everything he's done, but there is this part of her that favors all the good (despite being all fake) over the bad in the past. She still hates him, only now she's starting to like him as well. B doesn't help matters either. He likes to flirt with M, calls her pet names (such as sugar, baby, sweetheart, dear, darling), and just loves to engage in friendly banter. He is a very manipulative individual and everything he does, all those kind words and hugs, basically everything is fake from his side. He knows how to get what he wants (he's obviously had 2000+ years to perfect his art of manipulation). But M is starting to fall and a part of her thinks that at least some of the nice things about him could be real. The problem with this is that, as I said, it wasn't supposed to be that way. It's like the characters took over my writing. M already has a boyfriend whom she loves more than anything, and there's also a girl she likes as more than just a friend (but that's another story). Plus all the bad B's done doesn't make him any better a person in M's eyes, only somehow she's starting to see past it, a part of her thinking that maybe him being around her could change him, just like his company changed her. My question is: what do I do about this? I'm an amateur writer. This is only my third book. The first two books in the series had nothing like that so this is a whole new territory for me. M and B's "friendship" isn't meant to last for long, but it will have impact on her as well as on those she loves. How do I make sure it's done right? Any questions? Feel free to ask.