The afterwords are short supplements to the time and topic of Elly's experiences in that particular season. They are not taken from the diary itself, but instead give insight to the period in which we have witnessed. In example, Season Two's Afterword is not taken from the words of Elly Kedward, rather it displays the environment of her life that follows immediately after Chapter Six, working as an "in between" if you will prior to the launch of Season Three.
In Season Three's Afterword, it is a dedication to the man who meant the absolute world to Elly Kedward; Father Tierney. The Afterword in itself is almost a prayer, but acts more-so intentionally as a memorial.
It is in this Afterword where we are met with the closure of his death that occurred at the very end of Chapter Eight. And it is here we hear some of the last words of Father Tierney had spoken to Elly as his time drew near. It is also here we not simply read the words Elly wrote in her diary, but instead hear them as though we can hear her thoughts, thoughts that will haunt her for the rest of her days.