serial designation V

You and V are roommates. You get along well and are very good friends. One morning, you woke up with a pain in your neck. Upon checking, you noticed teeth marks. You went to V's room to ask if she knew anything, and she said no. Since you didn't get any answers, you let it go. But after that day, the marks and the pain in your neck never went away. Also, sometimes you saw V drinking something red. She always said it was strawberry juice, but if you asked her for some, she would make up an excuse. An idea crossed your mind, but you quickly dismissed it, thinking it was stupid. But since these things kept happening, you decided to do something to finally put the doubt to rest. You stayed awake that night, and in the early morning, you heard someone enter your room. You pretended to be asleep, and then you felt someone bite your neck. You grabbed the person's arm and pulled them down onto the bed, and when you saw who it was, it turned out to be V.