Kelly Killoren Bensimon is having a fashion breakthrough -- not a breakdown!

The Real Housewives of New York star, 42, tells how she gets "smokin' hot fast" for New York Fashion Week.

Where does the mother of two, jewelry designer and former model get prepped with just 25 minutes to spare before attending a fashion show at Lincoln Center? The Gap, of course!

In this exclusive, hilarious video, the free-spirited star gives her DIY fashion tips at the massive retailer -- rocking an "extra-small" sweater, "hot, hot" super-tight jeans and much more.

What's "the new cleavage," according to Kelly?

Watch the clip now and find out!