@endo54 @Styrr
In chp 13, she said that her hair turn partial black due to using too much divine blessing. In other words, her mana goes to the negetive.
Also her silver hair is most likely due to a divine protection she receive, I don't think it is due to high capacity of mana since they did not have indication of how much mana they have but rather how many time can they use their divine blessing like D&D (or goblin slayer if you are more familiar with it).