Ersa's former job was as a artificer, creating, appraising, and assessing wondrous items. Then she found her true calling as a mage. She still does appraisals here and there for extra coin, though.

It's heartbreaking, but Ersa lets the warrior know straight up what his sword actually is enchanted to do. It's not an epic weapon of destiny or something he needs to unlock the power from within. It's just a really good masterworks sword with a useful enchantment if you get lost in the wilderness.