The fortune teller's words about the woman in the desert are rather vague. Four completely different characters fit this description more or less. The worst of them is the Desert Witch, and if you meet her, it's a quick bad end.

In general, you don't need to focus on the woman. If you already have access to the desert and maps to move around this area, get to the desert city of Sunshine and explore it. There you can buy two additional maps, a headwrap, a new weapon, but the main goal is to find a map with a route to the slavers' hideout. In addition, you will need to get information about the tattoo on the slavers' faces.

There is another option - walk through the desert north of the city of Sunshine, meet a caravan and beat everyone up. As a result, you will get both a map and a tattoo at once. In any case, you will have to return to the slums of New Ark to apply this tattoo to your face.

Once you infiltrate the slavers' hideout, further events will lead you to the gold mine.