Mjoll the Lioness

Mjoll the Lioness is a female NPC in The Elder Scrolls V: Skyrim.

Interactions
When the Dragonborn meets her in Riften, she talks about her ire for the Thieves Guild. She is available to marry if the player possesses the Amulet of Mara.

She will also give you a quest if you agree with her about The Thieves Guild in Riften (or, if you disagree with her, wait a few nights, then return to her), where you will be given the task to find her sword named Grimsever in Mzinchaleft (Dwemer Ruin).

After successfully completing the quest, she can be asked to join you as a follower.

If for any reason at all, you harm Aerin, her 'savior', she will become moody, and not want to talk with you as often. If you are married when you kill Aerin, she refuses to talk with you whatsoever, stating how disappointed she is in you, and will walk away.

Marriage
The player can marry Mjoll If they possess the Amulet of Mara and after completing a personal quest for her. She can be both a follower and a spouse simultaneously. When married, Mjoll opens a Shop, and gives the player a profit of 100-300 Septims each day, and everyday that you don't collect from her, it adds up.

Although, even when wedded with the player, Aerin won't stop following her.