The portrait model is the actress, later also the instructor Agnes Mowinckel (1875-1963), who was active from 1899 to 1963. Regarding her and her hats, this is mentioned in SNL:

There are many anecdotes about Mowincke. She was always meticulously dressed, with an artist’s eye for colour composition; not least when applied to her hats. With small but refined tools, she created exciting creations of old and useful headgear. This had fatal consequences one day when she arrived at the crematorium for a funeral. In order not to be perceived as offensive with her rather showy headgear in relation to the situation, she handed the hat to the church servant. Great was her shock, however, when she saw him step forward and place his hat on the lid of the coffin.

Some may recognize this story from Odd Eidem’s (1913-1983) short story The Leaning Tower, which was filmed by NRK and can be seen here.