Good catch, Law!
Once someone knows spirit spells, they can be a healer, no matter what their current class is. So can a paladin be your only healer? Sure. It's easier if she starts as a priest, but you can convert over a warrior if you need to. And as Law pointed out, you can convert your priest to a ranger and still keep her as a healer.
Just do learn that cure poison spell before the Serpent Temple...
