…. if King Haakon chooses to have a Consecration.
I doubt Queen Mette-Marie would wear a tiara, I think she would go bare-headed. A cloth kokoshnik would be a copy of Queen Sonja but maybe she wants to keep that as a tradition.
But bareheaded is my guess, with her hair perhaps dressed in a way it won’t get disturbed when the Bishop lays his hands.
If she DID wear a tiara, which I doubt, I can imagine the diamond daisies as that tiara is so modest.