I'm terribly sorry, but if you're reading this note, it means I'm going to have to stake you. Sorry for the informal verbage, but there you are. No, no, darling, don't look now, but I'm stealing up behind you somewhere in this graveyard as we speak with a mallet and a pointy piece of wood to stick you in the heart with. Sorry. I know this is all very sudden and you might be a little upset, but you have to understand that you're undead, and I'm just doing what's in everybody's best interest. I have confidence that you would act similarly if I were in your position. It's not your fault, it's mine. I really should have made sure that your windows were properly locked, but hey, what can you do? I didn't even know what was going on, nobody tells me anything. Lucy, dear, what we have to accept is that you're not the same Lucy I proposed to. You want to suck my blood and it's a wonder you still know how to read. It's just not going to work out.
P.S. Do forgive me in advance for prying the engagement ring from your corpse. It was my mother's, you know.