Freya was one of the two Persocoms that were part of a series of Persocoms known as "CHOBITS". She was created because the wife of Ichiro Mihara (the inventor of the Persocoms), Chitose Hibiya, was unable to bear children. All was fine, until poor Freya fell in love with Ichiro. Freya eventually broke from the strain on her circuits. Before she "died", however, she transferred her memories into her younger sister (the other persocom in the "CHOBITS" series), Elda (also known as "Chii"), so that Freya would be able to protect her "sister". Freya is the mysterious Persocom that Chii sees when she closes her eyes.

(Source: Absolute Anime)