Taylor Swift, 'One Direction: This Is Us' Diss? [VIDEO]: 'Red' Songstress Worried About Harry Styles Badmouthing Her in '1D3D,' Will Write New Song About It

One Direction: This Is Us, the concert film/documentary directed by Morgan Spurlock that follows the boys of One Direction, premieres tonight. With that said, Harry Styles biggest ex-girlfriend, Taylor Swift, is reportedly biting her nails, waiting to hear if the documentary shows her in a bad light. In fact, one source says that Swift is ready for a big screen diss and will write a song in response if it happens.

The source explained: "Taylor Swift is 100% boy-free at the moment, but she is morbidly curious to see the new 1D movie. She just wants to make sure there aren't any little jabs at her. She really likes Harry and thinks he is a fun guy, but he was always a little immature, that's why it didn't work out. She just doesn't want any little jabs from him like the other guys in the band sometimes did. She really hopes that he's not talking anything shady to make her regret their fling."

"You bet there will be another song about him," the insider added.

Yikes! It looks like the news of Taylor forgiving Harry were not entirely true. At least not yet.

Mstars recently reported on how Swift will reportedly NOT be mentioned in the new documentary about her ex-boyfriend's band. Here is an excerpt:

There is a ton of hype surrounding One Direction's documentary/concert film This Is Us, hitting theaters later this year. One big topic of discussion is whether or not Taylor Swift and band member Harry Styles' relationship will be featured in the movie. To be blunt, no, she will not be featured at all, but that doesn't mean fans and others will stop speculating. Recently, director Morgan Spurlock has made it clear that he has had enough of these rumors, so he decided to speak out against them. 

"It gets frustrating for them at times, because suddenly stuff gets printed that isn't even true. I saw an article that said, 'Harry Styles demands Taylor Swift be taken out of the movie'," he said. "But by the time we started filming in January, they had already split up."