Fantasy novel from 1980s or 1990s set in a desert with fire elemental creatures. Female protagonist.

[Annabel]

I read this in my late teens, so late 90s, but I don't think it was super recent. I don't remember much, except that the protagonist is female and gets rescued by the other main character, who saves her by making her drink blood. I think she may have lost her memory but I am not sure. Her rescuer I think he ends up being under a false name. I remember there being creatures called fire elementals whose fire is magic and dangerous, but I think she ends up being able to communicate with or control them. I also remember there being an underground river, that was maybe poisoned? There was a love interest between the two main characters. Would love any ideas!