Grief is a strange thing, if you tightly love someone it comes as a huge blow when they pass away. Sometimes it is easier if they had been severely restricted or in on-going pain but it still takes effort to put things into perspective and go on without them.
But over time and life these deeply burning scars heal a little; they never go away, all major life lessons alter our psyche to make our views of the world our own. But sometimes the wires get crossed as well.
Sometimes when there is extreme dislike between close relatives this hate poisons the natural healing process that grieving brings. When an estranged relatives dies the person feel relief suddenly this conflict is over, then guilt that they do not feel remorse but rather satisfaction. This means over time they often dislike themselves for not truly loving a relative the way they were expected to, this keeps the wounds from healing over properly . . .
Sorry you lost your friend !