The Light Bringer - The Dragon Gate Series, #2

The power to heal only comes when she believes. On her quests to other worlds where elves, dragons, and magic are real, Anna can save the dying - and destroy the undead. But on an Earth where magic has awoken after a thousand-year sleep, the gods do not answer her. And yet other people are casting spells and healing the wounded, dealing death and bringing life. Some have come from other worlds, and now nowhere is safe. No one understands why it's all happening - or that Anna and her three friends mistakenly triggered the awakening.
To save everything that she loves, Anna must face her destiny as The Light Bringer, or the new reality they unleashed may destroy all life.