Hi @Jeansoo ,
I don't know if vampire break-ins on community lots is a bug or not, but I do know that my vampires also get break-ins on their home lot from time to time. You are right, vampires do not drink from other vampires. That means your vampire is not in any danger and that the event is rather pointless. When break-ins happen on community lots, I guess technically the "attacking" vampire can go drink from other Sims than yours. But I haven't seen it happen so far.
I also just go and talk to the "attacking" vampire to make the event stop.
