The WoL's aetheric signature has to be really complex (and unique). Start with our base Aether (including whatever comes from our classes and jobs), add in the effects of the Blessing, Echo, and whatever Midargsormr is doing to us, the 6 Crystals of Light we have, traces of every Primal we've slain (15 at this point), some of Hraesvelgr's Aether (we have to have retained a tiny bit from when we absorbed his Eye briefly), and whatever else we happened to have absorbed and kept (probably some of Nidhogg's Aether from killing him and using his Eye, traces of Ysayle's Crystal of Light, scars from Ascian and Primal attacks, and so on)

I'm sure Y'stola (and anyone who can sense Aether) can "see" us from malms away...