Chiko's... Clone...? Daughter...? Who knows.
She's an artificial CPU, created by cloning Chiko and modifying the clone, ripping her heart out and use the "CPU Memory" ( http://neptunia.wikia.com/wiki/CPU_Memory ) as a "Core"/"Heart" for the lifeless body.
The experiment worked, and she can also switch into her HDD form. To confirm that she won't turn into a monster, the disciple sent her to kill everyone in her way.
Some of these people were dear to Riju Kida, blinded by rage he tried to knock her down, he succeeded but he quickly fainted for the enormous damage he tanked before seeing her faint too.
But thanks to the boy's struggle, She began to suffer amnesia.
Chiko, growing a little bit of affection towards her, wanted her to escape from the scientist's hands and secretly helped Baron Clockwork steal her from him... this could also be understood as a form of... "payback" for the scientist's betrayal.
Inside the pocket dimension, Baron told her everything. From what she has done, how to behave as a good girl and basic information about combat.
Struggling to accept what she actually is, she tries, with the help of Baron, to become a "good girl" and ask forgiveness to everybody.

She's a very strong little girl. Aha.

Small spoiler: She will be adopted by Blu

The voice I believe fits her: "Kotoura":  https://youtu.be/HH4bYpItuRU?t=5m57s
If you believe you've got a voice that fits her, please, go on and show it to me!