u/Bvnnik

Hello! I’ve been trying to find the title of this book I read last year but I’ve had no luck. I’ll try to add all of the details I can remember. Just looks wise I think the cover was a mix of like, light blue / purple and periwinkle? Anywho the main character is a teen girl who is immune to this spreading virus, basically the whole world has shut down and the town she lives in is like closed off via glass I think? When people become infected with the virus they become single-minded murders. I think I remember they act friendly but quickly switch to describing violent fantasies on how they want to kill the person they’re talking to. I know MC has a boyfriend but I can’t remember if they break up. There’s like an island nearby and MC is told not to go to it but she leaves the town and goes anyways. I remember there was a lighthouse where her infected grandpa was staying, he keeps trying to kill her and she keeps him locked up and feeds him through like the little slip in the door. I also remember there’s a point where he escapes and tries to kill her again I think? Also MC gets pregnant somewhere in there and has a daughter and then there’s some plot twist at the end that the story is a retelling and the mother is talking to her now grown daughter? Sorry if this is really confusing I only have bits and pieces of it. Any help is appreciated. Thanks!