"Teen Mom" star Farrah Abraham is telling people she's not a party girl and she got a DUI last week because of an illness ... a little hard to swallow after looking at these pictures.

The photos were snapped in January at Halo Ultra Lounge in Omaha. The promoter tells TMZ, Halo was hosting a lingerie soiree ... and Farrah showed up with a bunch of slutty-looking girls, all wearing next to nothing.

Then the boozing started ... with Farrah guzzling straight from the bottle.

You'll recall, just one day after Farrah was arrested for DUI last week -- blowing nearly twice the legal limit -- Farrah tweeted, "It's amazing what people believe and make up!"

Farrah says the reason the breathalyzer registered a .147 is because she was coughing a lot and couldn't blow properly. 

That's what she said.