They must have renamed the painting recently. The one I got is called "Painting of a knight" (worth 1g). I sold all three items to her one at a time, exiting the conversation naturally each time. This completed the quest and I got XP and some random reward items, 1k gold, and choice of a lvl 18 gear, which was useless to me, but worth another 1k gold. So, not really worth it at level 19, but if you like sneaking around and getting past the sentries then may as well.