So, there are definitely signs of former habitation. A handful of high plateaus among the salt flats bear weather-beaten edifices that may once have been lighthouses. The dunes are peppered with the crumbling remnants of ancient villages. The canyons seem to be blocked off from the dunes with big walls of artificial stone wherever the walls of natural stone weren't enough, and behind that there are a few places where it looks like a big building was carved directly into a cliff face. The mountains have some old buildings, too, which are in better shape than the rest of the ruins but whose purposes are harder to identify.
Separately from all that, there are also a few places scattered around the island where a handful of plants cling to life around a dirty spring. These mostly seem to not be anywhere near the ruins, and there's no sign of those plants being harvested or even bug-bitten.
(A closer look at all the plausibly-man-made things in view will also reveal that there are on the order of a dozen cairns of stacked rocks scattered all over the island. Maybe more like two or three dozen. It's hard to say why they were built, but 'graves' is certainly a plausible explanation.)
The sole source of clean water on this whole entire island seems to be a small pool huddled amid the roots of that huge tree, southwest of her initial landing place. The tree, on closer inspection, is multiple different unfamiliar species of tree all growing together in a swirling braid, and four of the five of them are dead but the fifth has a green leaf or two remaining and isn't afraid to use them.
Also, it isn't quite what she's looking for, but she might like to know about the terrifying orbs of crackling red-violet energy that seem to congregate in loose clusters scattered all over the island, each one surrounded by formations of a scaly black rock that looks sort of like unusually feisty basalt. The orbs are about two feet across, range in height from about three to twelve feet off the ground, and occasionally strike their surroundings with flashes of red-violet lightning, which kicks up puffs of dust from the not-basalt and draws answering glimmers of light from nearby spars of a red-violet crystal that seems to exclusively grow in the orbs' presence. So, you know, there's that.