Nilsa Prowant -- who's been a regular on the "Jersey Shore" MTV spin-off for the past couple seasons -- got taken in by cops early Saturday morning in St. Petersburg after allegedly flashing onlookers in public ... and then kicking in a car window. Quite the night!

According to the arrest report, obtained by TMZ, Nilsa was observed by officers -- and a large crowd -- revealing her breasts from a balcony, telling folks down below to sneak a peek. 

The report says that Nilsa was told she had to beat it after that, but cops say she became belligerent and erratic. They also say that once she got into a car for a ride home, she started to lose it ... allegedly kicking the rear driver side window, until it shattered. That was the last straw, it seems -- witnesses say one cop said, "You got to go." 

She was arrested and booked for disorderly conduct and exposure of sexual organs -- both misdemeanors. Funny enough, it sounds like the cops were gonna let her slide for the alleged peep show ... but couldn't ignore the busted window. Go figure. 

Officers note in their report that there was an indication she was under the influence. 

Luckily for her, Nilsa's bail amount was set at just $400 ... and she walked free around 6:30 AM ET. Unclear if cameras were rolling for this incident, but something tells us they might've been ... the show is reportedly in the middle of filming right now, and airs in the fall.