If the shaman is a living creature, she reacts to positive and negative energy as if she were undead—positive energy harms her, while negative energy heals her. If she's an undead creature or a creature with the negative energy affinity ability, she gains a +1 bonus to her channel resistance. At 8th level, if she's a living creature, she gains a +4 bonus on saves against death effects and effects that drain energy; if she's an undead creature, her bonus to channel resistance increases to +2.
At 16th level, if the shaman a living creature, she takes no penalties from energy drain effects, though she can still be killed if she accrues more negative levels than she has Hit Dice. Furthermore, after 24 hours any negative levels the shaman has are removed without requiring her to succeed at an additional saving throw. If the shaman is an undead creature, her bonus to channel resistance increases to +4.