Awkward ghostly love triangle: Character dies while either engaged or very newly married and sticks around as a ghost, but their partner isn't interested in doing the Herbert & Winnie Fudge thing. The partner goes on to court someone else, which the ghost is totally fine with — really, it's inconsequential — honestly, they hardly even think about their old life anymore, they're too preoccupied with spirit things anyway! They're living their best afterlife all on their own!

They're also kind of stalking the new romantic interest, though.