Complex sentence: Yvonne is ultimately converted into a Cyberman during the Series 2 finale, however she manages to gain control of her metallic body and is able to fight back against her creators, buying the Doctor and Rose Tyler the time they need to close the breach.
Split into simpler sentences: Yvonne is ultimately converted into a Cyberman during the Series 2 finale. However, she manages to gain control of her metallic body and is able to fight back against her creators, buying the Doctor and Rose Tyler the time they need to close the breach.