Ask any generator for the same person twice and you get siblings. Consistency is the hardest problem in generated film, and it is not solved by better prompts.
Why it drifts
A text description is a wide net. "Woman, thirties, dark hair" matches millions of faces, and the model picks a different one each time. Lighting, angle and style pull the result further.
Lever one: references
Give the generator images, not adjectives. The character bible stores up to four reference faces and passes them to every scene. This alone removes most of the drift.
Lever two: variants
A single front-facing reference does not help a profile shot. Pose variants, generated once from the bible, cover the angles your scenes need.
Lever three: anchor frames
Approve a storyboard frame where the character looks right, then generate the video from that frame. The clip inherits the face instead of reinventing it.
Use all three and drift becomes the exception you fix, not the rule you fight.