This is the 5395th most frequent Spanish word.
millonaria
A woman who is a millionaire.
‘Millonaria’ is used here as an adjective to describe a woman who has amassed significant wealth.
Ella se convirtió en una mujer millonaria tras el éxito de su negocio.
She became a millionaire woman after the success of her business.
In this sentence, ‘millonaria’ modifies ‘donación’, indicating the donation was of a very large amount.
Hubo una donación millonaria al hospital local para mejorar sus instalaciones.
There was a million-dollar donation to the local hospital to improve its facilities.
Here, ‘millonaria’ functions as an adjective describing the lifestyle as one associated with great wealth.