This page in our guide to GreedFall contains a walkthrough for The Queen's Farewell, Siora's side quest.
Where to start the quest?: You must complete Siora's previous mission.
Talk to Siora about her mother's funeral and offer to help her. Go to Eseld and talk to the woman. Then, go to the tumulus with Siora. Along the way, you will find that monsters have invaded the area - defeat the creatures and destroy their nests. Go to the mound. Siora asks you to craft two items that will be used in the funeral - 2 censers and mortuary potion.
Both items can be crafted at a workbench. Place the items on the corpse of the Queen and let Siora say goodbye to her mother.
This completes the quest - you get +1,600 XP and get 3 reputation points with Siora.