princess vs blue blood

princess and blue blood both are nouns.

Word	Noun	Adjective	Verb	Adverb
princess	Yes	No	No	No
blue blood	Yes	No	No	No

As nouns, blue blood is a hypernym of princess; that is, blue blood is a word with a broader meaning than princess:

princess: a female member of a royal family other than the queen (especially the daughter of a sovereign)
blue blood: a member of the aristocracy

Other hypernyms of princess include aristocrat, patrician, adult female, woman.

princess (noun)	blue blood (noun)
a female member of a royal family other than the queen (especially the daughter of a sovereign)	a member of the aristocracy