Just how old is V? Dementia is a real possibility, my grandma has some interesting days. My great grandmother used to hide plates of food in drawers, and believed that the people in the tv were really in the room, would talk to them,or yell at them to get out of her house.
Another possibility is minor stroke... have you talked to her about seeing a doctor? Or do you feel that would overstep the bounds of your relationship with her? Is it possible to get in touch with her family and talk to them about the problems V is having? My great aunt had a blockage in a blood vessel in her brain caused by cholesterol, and she used to do some interesting things too. She accused her husband of cheating on her (they're in their seventies), she used to call my dad all the time to come and take a look at her mulberry bushes (which were long since cut down, and were on the farm that she hadn't lived on in 40 years). There are a number of things that could be happening to V at this point, and I think that if this is something new for her at her age, it is most likely dementia/alzheimers and not schizophrenia. I do think it's important that V gets some medical attention, and unfortunately she's not likely to ask for it on her own. If you can get in touch with her family, please do so. Even at the risk of having her get mad at you. She doesnt have to like you for you to help her, right? I'm sure her family will appreciate it, just be tactful and say that you are worried about her. In the mean time, it's really good that you're keeping an eye on her, good for you. You're a good neighbour.