@FrenchMontana / Instagram 1 / 9
@FrenchMontana / Instagram 1 / 9

This is one one way to add insult to injury!

Taylor Swift's nemesis and her ex partied together in Las Vegas on July 23.

Kim Kardashian West, 35, and Calvin Harris, 32, hung out at a pre-birthday bash for Jennifer Lopez following J.Lo's "All I Have" show at Caesar's Palace -- and rapper French Montana posted the photo proof afterward.

The reality star and the Scottish producer-DJ also spent time chatting at the party, reports Us Weekly. "Kim and Calvin did talk and interact, smiling and chatting for awhile," a source told Us.

Kim and Taylor have been feuding since February when Kim's husband, Kanye West, 38, released his song "Famous" -- in which he takes credit for Taylor's celebrity status and calls her "that b----." At the time, Taylor denied Kanye's claims that she'd given her approval to his lyrics and later took aim at him in her Grammys Album of the Year acceptance speech.

In June, Kim went on the offensive in GQ, insisting Taylor not only signed off on the lyrics but that she and Kanye had the video footage to prove it.

On July 17, Kim released a few snippets of that footage in which Taylor can be heard seemingly signing off on some of Kanye's lyrics, although she hit back to insist that the rapper never told her he planned to publicly brand her the "B" word in others and accused the couple of "character assassination" and having "secretly" recorded her.

Just days earlier, Calvin -- who split with Taylor in late May after 15 months of dating -- had taken to Twitter to accuse his ex and her team of trying to make him look bad after Tayor's rep confirmed that the pop star had written the DJ's big summer hit, "This Is What You Came For," under a pseudonym.

Curiously, on July 22, Calvin quietly deleted his Twitter rant against Taylor, including the jaw-dropping part about how Taylor had tried to "bury" rival Katy Perry.

Kim was in Vegas to host a nightclub party, while Calvin was there for his ongoing DJ residency.

He shared a video of himself dancing with J.Lo -- who turned 47 the next morning -- on Instagram, captioning it, " Happy birthday Jennifer Lopez, legendary icon - and your show in Vegas is next level."

Other guests at J.Lo's party reportedly included Iggy Azalea, soccer star Cristiano Ronaldo, John Stamos and Maria Menounos.

Taylor, 26, meanwhile, has been keeping a low profile following her Calvin and Kimye feuds.

She flew back to Los Angeles with new boyfriend Tom Hiddleston, 35, after spending the last few weeks with him in Australia, where he's shooting "Thor: Ragnarok," but seemingly did not accompany him to San Diego for his Comic-Con appearances on July 23.