According to her biography, Erin is a new resident to Sunset Valley in accordance with a transfer in her job in the Military career, level 4. Because she is a new resident, the only Sim she knows is her employer, who may be anyone working in the military at the start of the game (often Jack Bunch).
Her skills consist of Athletic 4 and Handiness 1, and her life essentially is her career as inferred by such skills as well her initial wish to work out. Her inventory starts out with a copy of the book Totally Preggers: An Expecting Mother's Tale. She lives in a house called Cottage Cheese in the poor area of town, near the local gym.