Why won’t someone just let go of a dead person?

Don't be so unempathetic
My dad died many years ago but I still miss him when I think about him
People deal with things differently
No matter how old I get it'll still make me sad to think my dad missed all of it

No one just gets over stuff..i lost both my parents 8 years ago and still grieve everyday for them its not a choice its feelings we have no control over

There's a similar situation going on with a friend of mine. Her dad passed away about 5 months ago and she posts pictures of him daily on FB. It's getting too much I don't get it either, if she stops doing that she won't forget him. Actually that's the issue, they think that letting go equals forgetting. Humans do forget though it's very natural plus again it's not like you're going to forget completely they of course will live in your memories forever.

You won’t ever understand until you are in the situation

What do you mean by ‘let go’ - people grieve in different ways & in their own time & your friend will always have the precious memories of her sister & should be able to talk about her whenever she likes

It was her sister I don't think people ever get over that stuff a brother or family cat I can understand but a sister; do you not have a heart?

So you have never lost anyone before? Nobody ever left or died and you never got over it?

some grief is complicated, meaning it actually causes lingering mental health issues. sometimes, people need therapy to process and move on.

That really is extreme and sounds like she may need professional help.

Relationships are complicated...seems she had unfinished business.