Sylvia told Pylia, "Apparently someone's heart was changed into a gemstone that would power this thing, and the robot was once...flesh before the metal was placed on him," When Shortfang mentioned the ring, she accepted the ring, and answered Pylia and Shortfang, "I'll try wearing it then," She then placed the ring around her finger. 

She then asked Shortfang, realizing something, "Oh yeah! Shortfang, do you still have the red gem from the skeleton's dagger?" Maybe that red gem was a heart.