Someone overzealously enthusiastic towards something. Wanting to be recognized for your love of something.
I know everyone loves chocolate, but she is a chocolate passionista!
A fervent popular activist. Someone who gets very animated and active over fashionable causes such as the political prisoner du jour, climate change, Darfur or whatever is fashionable to be outraged about. Heart in the right place, and will tell you all about it whether or not you want to hear it.
Usual, gave me on Darfur when she dropped off some low-energy light bulbs as a gift.
She's such a passionista.