Rousseau was a powerful woman of French origin. She was renown for her physical abilities, cutting a chiseled 6'2" frame, with tanned skin and hair that must have been dyed blond often tied back.
Rousseau commanded with intimidation, Callus and Curtis were among the few to not be afraid of her. She constantly bragged about her sniping skills, even though she was more skilled in assault, as Curtis concluded from battlefield observation. When Callus fell, she assumed Curtis had been killed as well. She went off after Ambrose herself. She managed to catch him alone, and the two dueled. Both were N7 graduates, both were skilled hand-to-hand combatants, but Ambrose had something she didn't, biotics. Ambrose's biotic abilities gave him the upper hand, and he won and escaped from Aldrin with Jolt in tow.