millionairess vs rich person

millionairess and rich person both are nouns.

Word	Noun	Adjective	Verb	Adverb
millionairess	Yes	No	No	No
rich person	Yes	No	No	No

As nouns, rich person is a hypernym of millionairess; that is, rich person is a word with a broader meaning than millionairess:

Other hypernyms of millionairess include have, wealthy person, adult female, woman.

millionairess (noun)	rich person (noun)
a woman millionaire	a person who possesses great material wealth