You may need it to be a work in progress if the client wants to go really light, but tgis all depends on whether shes got colour on already? How the condition of her hair is?
Afro hair can be incredibly fragile and can become very damaged if this process is rushed.
As the other geeks said, you'll have to see what level you can safely lift it to be for choosing the correct toner. Is it virgin hair? How much hair does she have?
I think youll need to plan for every eventuality. X