Hilde is a NPC in Divinity: Original Sin 2.
Interesting feature I found regarding both Hildur's Plate and the Kalias Stunner sword, the level of the armor and weapon are actually based upon what level you are the first time you interact with their shop. I was doing a murder everyone playthrough and I used deathfog to kill the group encounter with Alexander and Dallis at the start of Fort Joy, then I did a couple other things and got to level 4 by the time I interacted with Hildur and Kalias, and both of their unique items were being sold at level 4 instead of level 2 with much stronger stats. I'm not sure if this is intended with every unique item you come across that gets sold in a shop, but this is just something I found interesting to come across.
If you speak to her with an OUTLAW character like Sebille, she'll lower her prices slightly.