When the game starts, her relationship with her roommates is only at the acquaintance level.
Erin actually has a history that extends beyond her life in the Singles Household. She is the younger sister of Loki Beaker, who lives in the Beaker household. Their parents are Bjorn Beaker and Gundrun Beaker, both deceased and also of Strangetown. She was born when her brother was a child.
It is suggested that she and her brother have Scandinavian ancestry, (Norwegian, possibly), due to their last name and characteristics.