You cannot select a female Spartan model in Halo: Reach. The game only offers the male Mark V(B) / Mark VI armor permutations. No female voice, hitbox, or model exists in the base game.
SpartanValkyrie, LunaWolf, PinkPlasma).Full body type selection: "Body Type 1" (masculine) / "Body Type 2" (feminine) / "Body Type 3" (broad). Independent of voice. Armor fits all. This is the first Halo with official female Spartan representation.
Reach (2010): No female model. Express via cosmetics, voice, community. MCC PC: Mods exist (custom games only). Infinite: Full support.