"James motioned to a boy named Craig. A girl named Erica. Like James, they'd been healed by the morphing process. Like James, they were pretending to still need care. How they managed it, I don't know. Craig and Erica were, in effect, James's lieutenants."
Erica was a young girl recruited to be one of the Auxiliary Animorphs, became one of James' lieutenants, and was one of only three recruits to be healed by the morphing process.
The Auxiliary Animorphs
"Slowly our team formed a line. Grizzly. Gorilla. Tiger. Andalite. Hawk. Wolf. Then James's team. Lion. Crocodile. Bobcat. Bull. Then Craig's team. And Erica's. Slowly the visser's attention was caught. Maybe I imagined the look of fear that flitted across his enigmatic Andalite face as he surveyed our forces. Maybe not. But for the first time since this war had begun, it looked like a fair fight."
When the Animorphs began looking for new members, Erica was one of the recruits selected by James. James, Craig and Erica were the only three to be healed by the morphing process. Because they had been healed and could protect others, Craig and Erica both became lieutenants to James. Because of this she became a mentor of many members, in particular Jessie and Zoe.
"I felt sick inside. I should do something. I should stop this. That was the auxiliary Animorphs down there on the ground dying. Burning."
Erica, along with the rest of the Auxiliary Animorphs died in the final battle against the Yeerks' Pool ship. They had sacrificed their lives to assist Sam Doubleday's ground force as the original Animorphs invaded the Pool ship. Jake heard Visser One gleefully order the Pool ship's gunners to kill any animals in the fight below, until the gunners report none are left.