Jensine is a Nord who owns the shop Jensine's "Good As New" Merchandise, in the Imperial City Market District. She is also the head of the Society of Concerned Merchants, a merchant organization set up to allow for better trade amongst the merchants in the Market District.
She also initiates the quest "Unfriendly Competition," which is about Thoronir and The Copious Coinpurse. She is angry because Thoronir offers exaggeratedly low prices, and she thinks his goods are stolen items.
Jensine wears a teal long-sleeved shirt with a brown, rugged skirt (which is lower class apparel). She also wears sandals, which the Hero wears as a default in jail, or during the tutorial at the start of the game.
While exploring the Temple District in the Imperial City, Ruslan or his friend Luronk gro-Glurzog may ask for a few Septims to hold them off until payday. Whether or not money is given to them, they will explain that while at Jensine's "Good as New" Merchandise a captain of the city guard came in and accused them of theft. Despite their innocence and Jensine defending them, the guard told them to hand over their money or face time in the Imperial City Prison.
Head over to Jensine's shop and ask her about Thoronir, and she will tell the Hero that she is the head of the Society of Concerned Merchants. This society is meant to help out all the merchants in the city by working together to keep all business practices fair.