Jen Taylor
From Halopedia, the Halo wiki
Jen Taylor or Jenn Taylor is the voice of A.I. Cortana in both Halo 1 and Halo 2.
Dimensions
Height:is 5' 6" (1.68 m).
Summary
Jen Taylor is best known for her work as Princess Peach, Toad, Toadette and other characters in several Nintendo games since 1999, and the voice behind Cate Archer in No One Lives Forever 2. In 2004 she also appeared in the feature film Inheritance.
It is expected that Jen will return to voice Cortana in Halo 3. Also she'll voice Jessica Cannon in the upcoming episodic FPS Sin Episodes.