have you tried talking to the NPCs at the Sanctum of the Twelve. While I wasn'married i needed to remove the quest, in case I wantednto marry someone in the future. I talked to an NPC and the quest was erased from my log. I would assume divorcing is similar. Whether you need the other peeson or not I don't know; I didn't. I will say that divorce is probably already in the game since they tell you during the quest if you want to marry someone else you need to anull the previous marriage.