Teresa Espinosa, once a backup dancer for Britney Spears, has publicly addressed cheating allegations made by Kevin Federline.

In his upcoming memoir, titled “You Thought You Knew,” Federline—who was married to Spears from September 2004 until July 2007—accuses Spears of having an affair with Espinosa back in 2004.

Espinosa, who was part of Spears’ team during the “In The Zone” phase, which led to the Onyx Hotel Tour, took to Instagram on Thursday to stand up for the pop star.

“During that period (2003 to 2004), I was acutely aware of the whirlwind that surrounded Britney’s life simply by being near her,” Espinosa shared.

“The paparazzi were relentless, following her every move. She couldn’t even breathe or sneeze without someone trying to capture a piece of her radiant spirit.”

Espinosa admitted she “didn’t have the words to explain [her] experience with” Spears, but could sense she “was lost” and wanted to feel “normal” — without “the world watching her every move.”

One night, Espinosa invited Spears to join her and her friend to go to Joseph’s Café, “THE club to go to in that era.”

Espinosa recalled being “frantically chased by paparazzi the whole way to the club,” calling the drive “dangerous and super crazy.”

Upon arriving, Espinosa saw her “friend Kevin Federline,” who was also a backup dancer at the time. While Espinosa and Federline “lived in the same quadruplex,” he “just happened to be there that night.”

“When I saw Kevin, I thought, ‘Kevin is cute. I should introduce them,’” she thought to herself. “I’m not exactly sure how that innocent introduction turned into more than just a simple hang, and that’s not my story to tell.”

Shortly after joining Spears and Espinosa on the Onyx Hotel Tour, Federline and the singer went public with their relationship, tying the knot just a few months later.

“I feel blessed to have shared the stage with her all over the world. She allowed me to live my dreams as a professional dancer and eventually asked me to choreograph the ‘Outrageous’ music video, which was never fully completed because she hurt her knee on set,” Espinosa told her followers.

She concluded her message, “And so here’s my take: NO ONE will EVER know what it’s been like to walk second in her shoes.”

Federline, 47, claims in his tell-all that it was on this tour that he caught Spears, 43, and Espinosa “full-on making out” and “going at it” in a hotel room in Amsterdam.

Though the Grammy winner — who shares sons Sean Preston, 20, and Jayden James, 19, with Federline — has not yet specifically addressed the cheating allegation, she did blast him on Instagram for “gaslighting” and “hurting” her with his “white lies.”

Her rep echoed those sentiments in a statement to Page Six, saying, “With news from Kevin’s book breaking, once again, he and others are profiting off her. Sadly, it comes after child support has ended with Kevin.”

According to Spears’ rep, “all she cares about are her kids … and their well-being during this sensationalism.”