'Jersey Shore' Star Deena -- FURY at Boob-Flashing Look-alike at Mardi Gras

Deena from "Jersey Shore" says she's NOT a Mardi Gras booby flasher -- and claims she's getting a bad rap thanks to a sluttier doppelganger who looks just like her.

TMZ obtained video of a girl -- who looks EXACTLY like Deena -- partying her face off, lifting up her shirt and flashing her boobs down in New Orleans this week ... and people who witnessed the event first hand were convinced they were observing authentic MTV tatas.

But the REAL Deena tells TMZ it's not what it seems ... explaining, "I'm in Jersey right now ... plus if I were down in Mardi Gras I would NOT be showing off my boobs or any of my goods."

She continues, "I've been trying to work on changing my image especially since I want to be casted on 'Dancing with the Stars.' I get imitation is a form of flattery but this is definitely not the imitation I can ever hope for."

Fine. No beads for you.