Speaking with Esmeralda, we've come up with a small bit of background of how they know each other a little while Samantha is still in chargen:
Esmeralda came into the talismonger shop where Samantha works as the assistant to buy magical supplies. Samantha and Esmeralda began to chat and after a few meetings like this they went out to the Barricade for a beer to talk and get to know each other. During this time Samantha learned that Esmeralda is some type of Great Mother Shaman, has a 'man' and has been around the blight for a while, but really has not real exciting things going on in her life.
It's during this conversation that a gunfight breaks out in the street outside the Barricade and of course, everyone files out to check out the carnage. Some gangers have been shot up and Samantha moves off to start using her healing magics to treat the wounded without question.
That's about all the history we've worked up between Samantha and Esmeralda.