Well she is still absolutely beautiful regardless of tail colour
Unfortunately once the hair follicle has lost the black pigment from excessive drying, no amount of conditioning or anything for that matter will get the black pigment back.
Conditioning will only help to prevent further excessive loss of pigment. The hair underneath is protected by the hair on top so less drying occurs, much the same as human hair
Any conditioner that helps keep moisture in the hair follicle may help further bleaching but unfortunately once the damage is done, nothing short of dying will bring that pigment back!