Wallace would be arguably the most appropriate, as he is the person she has leaned on the most (of the likely candidates) this season, and probably the person she would want to unburden herself to most of all. That said, I agree that it is unlikely to be him. Realistically, it would be unlikely to be Logan either, as his father was just arrested for murder and Logan is a juvenile. It's not like the cops wouldn't be making every effort to find him. And Veronica's been too up-and-down in her emotions about him to realistically feel anything so quickly, I wouldn't think. Unless all she felt is the need to apologize for suspecting him. Same goes for Duncan. Weevil? Can't get there. So, overall, I conclude that there is nobody at the door, and Veronica has gone insane. Next season takes place in an asylum.