Newly single Taylor Swift may be at odds with her ex boyfriend Calvin Harris -- but she knows a good tune when she hears it, especially when she helped write it!

The pop star posted a video singing along to the track "This Is What You Came For" while watching gal pals Gigi Hadid and Martha Hunt strut their stuff during the TommyXGigi (Tommy Hilfiger's fashion collab with Hadid) NYFW show on Friday, September 9.

Tay posted the video and wrote, "SO PROUD OF YOU GIGI!!!! That show was INSANE. Congrats to Gi, Tommy, and all the girls who just owned that runway!!"

Of course, if we didn't know the backstory of this chart-topping song and all the drama rama it caused over the summer — we'd think this post was just an adorable Instagram, but we know there's more behind this music …

In July, Swift revealed that she actually wrote the lyrics and melody to the Rihanna-sung song under the alias Nils Sjoberg.

Previously, the Scottish DJ had shut down any talk that he would collaborate with his hit-making girlfriend.

However, a month after their break up, Swift's rep confirmed that Swift worked on the track and the Scotsman was not happy, taking his fury to the place where celebs go when they can't hold their tongues (or their thumbs) -- Twitter.

In defense of criticism (and maybe because he was a bit butt-hurt that his ex had started dating Tom Hiddleston two weeks after their own split), Harris tweeted, "I wrote the music, produced the song, arranged it and cut the vocals though.'

The 32-year-old added, "And initially she wanted it kept secret, hence the pseudonym. Hurtful to me at this point that her and her team would go so far out of their way to try and make ME look bad at this stage though."

Oh but he didn't stop there, writing, "I figure if you're happy in your new relationship you should focus on that instead of trying to tear your ex bf down for something to do."

Ouch!

Of course, the EDM superstar eventually changed his tune, explaining recently to British GQ that he regretted his tweets.

He told the mag, "It was completely the wrong instinct. I was protecting what I see as my one talent in the world being belittled."

The DJ went on and said, "It felt like things were piling on top of me, and that was when I snapped. I'm not good at being a celebrity, but when it ended, all hell broke loose. Now I see that Twitter thing as a result of me succumbing to pressure. It took me a minute to realize that none of that matters. I'm a positive guy."

We're glad that he can apologize and glad that Tay could enjoy the song she co-wrote!