"Boardwalk Empire" star Paz de la Huerta was arrested last night after she allegedly threw a glass at former "City" star Samantha Swetra at an NYC party on Sunday ... and then socked her in the face.

Sources familiar with the situation tell TMZ, it all went down at The Standard hotel -- after Paz and Samantha got into it over Samantha's male friend ... we're told Paz was hitting on him and Sam got defensive.

According to sources, Samantha made a few snide remarks about Paz's level of inebriation ... and Paz got PISSED, throwing a glass and punching Samantha in the face.

We're told pieces of the glass became lodged in Samantha's leg, and her friend helped pick out the bloody shards ... while Paz was escorted out by security.

Samantha filed a police report this morning with her attorney Stephanie Ovadia.

Credit: TMZ

Roxy Olin and Samantha Swetra attend the Target Kaleidoscopic Fashion Spectacular exclusive VIP viewing party at The Standard on August 18, 2010 in New York City.

Credit: Zimbio

Roxy Olin and Samantha Swetra attended HP Celebrates Collaboration With The Much Anticipated "Sex and the City 2" after party at Bergdorf Goodman's on May 25, 2010 in New York, City. Also pictured, Designer Vivienne Tam.

Credit: Zimbio

Whitney doesn't follow Kelly's advice and brings Roxy along to a Glamour magazine shoot, and it almost ends in disaster. Erin and Olivia compete to be featured in New York's biggest gossip column.

Kelly tells Whitney she'll be in a Glamour Magazine feature but discourages her from bringing Roxy to the meeting.

Whitney is excited to hear about Glamour but insists she wants Roxy there with her.

Whitney has a great initial meeting with Glamour and tells them Roxy will join her on the follow-up meeting to help pull the look.

Erin chats with Robbie's assistant, Seth, about Olivia's party schmoozing.

Olivia accepts another invitation from Joe to attend a party for designer Elie Tahari and the department store, Bergdorf Goodman.

Whitney asks Roxy to go with her to the Glamour Magazine meeting despite Kelly's objections.

At the Elie Tahari party, Olivia poses with Tahari, and ELLE Editor-in-Chief, Robbie Myers.

Whitney and Samantha celebrate Whit's successful networking with Bergdorf buyers and gossip about Olivia at the Tahari party.

Neel goes straight to Olivia and Joe at the party to get some gossip for his article.

Roxy shows up late to the Glamour meeting and makes matters worse when she likens one of Whitney's looks to that of a 'hooker.'

Whitney is embarrassed following Roxy's foot-in-mouth actions at the meeting.

Erin and Olivia attend an ELLE meeting and find out the magazine got a mention in Page Six, but not for the gossip Erin started.

Roxy and Whitney are called in to Kelly's office who chastises Roxy for her comments at Glamour.

Whitney tells Roxy that her choice of words weren't cool, and put her reputation at risk.

Roxy stays true to her comments and refuses to apologize to Whitney.

Credit: MTV

Linda Fargo and Elle's Joe Zee hosted a stylish affair for Elie Tahari's Spring 2010 and handbag collections last night at Bergdorf Goodman. In attendance were The City's Whitney Port, Olivia Palermo, and Samantha Swetra.

Credit: Guest of a Guest

Samantha Swetra and Freddie Fackelmayer attend the I Want Now fashion show benfiting Haiti at Tenjune on March 25, 2010 in New York City.

Credit: Getty Images

Samantha Swetra celebrated her birthday as Lo Bosworth was hosting LIV at Fontainebleau Friday night, March 12, 2010, in Miami, Florida.

Credit: StarTraks Photo

Adrienne Bailon, former City star, Erin Lucas, and City star, Samantha Swetra, sat front fow at the Walter Fall 2010 fashion show at Stage 37 on February 16, 2010 in New York City.

Samantha Swetra gets her make-up done backstage at the Walter Fall 2010 fashion show at Stage 37.

Erin Lucas and Samantha Swetra exit the Walter Fall 2010 fashion show at Stage 37 on February 16, 2010 in New York City.

Credit: Getty Images