Upon talking to Ysolda as part of the quest, the Dragonborn will find out that a marriage proposal was made to a woman met while intoxicated. After seeking the woman out, Moira turns out to be a Hagraven, who says that she is waiting to consummate the promised marriage. When asked to return the wedding ring, she becomes hostile, claiming that the player wishes to give the ring to "that hussy Esmerelda".
Moira may also put out a contract to thugs if the ring is stolen from her or if her sister Anise is killed. The contract will say the Dragonborn is a thief in either case.
If, after completing A Night To Remember without going to Witchmist Grove, one goes there, she will be standing outside the shack and will not be hostile. She cannot be talked to and will have the Wedding Ring in her inventory.
Prior to the activation of A Night to Remember, there is a witch at Witchmist. It is possible that Moira was this witch, and turned into a hagraven after the quest started.
She shares her name with the shopkeeper Moira Brown from Megaton in Fallout 3, another game by Bethesda. This may be a coincidence, or it could be a nod to Moira Brown who may become an intelligent ghoul if the bomb in Megaton is detonated.