Somewhere in the distant past, Lydia's mother's(A half-elf herself) people dallied with a fey creature and a child was produced. After some generations, in elven years, that is the fey blood has thinned to the point that only one or two  per generation shows any sign of it at all. It skipped both Lydia's mother and grandmother (who had a dalliance with a human merchant). The abilities are usually linked either to the forested regions, but as it's the first time that a half-elf has shown the blood, it was bound to an urban environment; the area of her upbringing.<br/><br/>As it was explained to me, in race building, the perception bonus was a 2 bp item, so they more or less trade out. If you don't want to allow it, it's cool, I just thought that healing was tight for the party and one more healing spell might be nice.