I think it's something to do with him. Her hair is the color of his hair and eyes. I think he is what gave her the willpower to create this world. So her having this hair color means everything, even the system window is blue. Maybe all of her hair will turn blue or something(I don't think it's likely)?
I like this theory and I'm sticking with it. If them both having white hair bothers you I'm sorry, but compare it to a romantic relationship between characters who were both born to have black hair. She wasn't born with this hair color she earned it and we the audience can see it.
(I still feel the way you do sometimes about characters sharing to similar of color palettes but this case is different)
There better be an apology after this.
And I'm not hating on the MC's hair or anything, but can we not make her a white haired person too. It kinda feels like they're related huhu ╥﹏╥