It's episode 9 : Hostile Makeover / Grid Iron Glory
Hostile Makeover: The Cluster infects Jenny with a microscopic nanobot that transforms Jenny into a Neanderthalish, robotic she-thing. The change is slow, appearing to be some sort of robotic puberty. Bolts appear on her face like zits, her voice becomes deeper, and she has growth spurts. Will anyone figure out what is happening to her before the changes are irreversible?
Source: TV.com
http://www.tv.com/my-life-as-a-teena...=subtabs;guide