Unprincessly

She not only will never permit any one to touch her hair, which she always dresses and arranges herself, according to her own particular notions of grace and beauty, a thing which, I venture to think, and may perhaps suggest, is very unladylike, not to say unprincessly, savouring of plebeian independence, and low, artist-like individuality of taste, wholly unbecoming her distinguished rank and station;—[…]

Source: wiktionary

Some of the papers, with questionable taste, present Mrs. [Alice Roosevelt] Longworth to their readers as the American “Princess.” There is nothing in her ways, bearing, or appearance to warrant the epithet which I give, as printed, in inverted commas. Her natural, unconstrained, yet lady-like, manners are the opposite of princessly. She has chic, which, too, is unprincessly. Most princesses are shy when they find themselves with ordinary people.

Source: wiktionary

Switching from crying to laughing, Gabriella snorted—the most unprincessly sound she had ever made.

Source: wiktionary