The singer, a supporter of Mr Trump, told Politico: "I'm wearing this silver suit and stretchy trousers and, after the photo, he smacks my ass really hard".
"It was completely demeaning and shocking", she told Politico.
It was there that the pair took a photo together and Lewandowski slapped her on the butt.
"I said, 'Watch it.' Half-joking, I said, 'I can report you for sexual harassment, '" Villa added.
Politico said it reached out to Lewandowski for comment but did not receive a response. "I wanted to play it safe and avoid the drama", Villa said.
"Here's the photo of @CLewandowski_ seconds before he slapped my ass, I told him to stop, and then he did it again", she wrote.
"Corey laughed in my face and ran away", Villa told Politico, which corroborated Villa's account with a witness.
Lewandowski remains in Trump's close circle, and he recently published an inside look at the campaign, titled "Let Trump Be Trump: The Inside Story of His Rise to the Presidency".
In 2016, Lewandowksi was arrested for assault after grabbing a reporter's arm at a campaign event, but the charges were later dropped. Campaign press secretary Hope Hicks said that despite video evidence to the contrary, the accusation was false.
While Lewandowski was sacked by the Trump campaign well over a year ago, his name has recently been floated for a staff position in the West Wing, as other presidential aides are planning their exits. "As a matter of fact, I have never even met you". But Villa said another reveler pushed her toward him and she ended up standing next to him and posing for a picture, despite his seeming lack of interest.
All things considered, he's back in the news once more. Villa said she had been enjoying herself at the party. "It's how every woman feels when she is sexually harassed".
It was only after the eyewitness reported it to Politico that Villa agreed to share her account of it. But her relationship appears to have soured with the president's former campaign manager.