Previously, she co-wrote Kellie Pickler's "Best Days of Your Life." Plus, Swift rarely makes guest appearances on other artists' songs, though she covers many in her live shows.The last known collaboration she has done with a romantic partner was "Half of My Heart" with John Mayer in 2010.
In 2014, Harris' ex-girlfriend Rita Ora dealt with this issue.
The pop singer claimed that Harris blocked the televised performance of her song "I Will Never Let You Down" at the Teen Choice Awards, a song Harris wrote and produced entirely. so [he] has to approve anything TV-wise," she told Ryan Seacrest in an interview.
What are Taylor Swift's rights as a songwriter?
As a co-writer of the song who provided lyrics and the melody line, Swift could prevent the song's usage in television and film, but not live performances.
Scroll down for a complete timeline of this 21st century war!
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Katy began dating Taylor's ex John Mayer in 2012, but the two women remained cordial. It's no secret that Taylor knows how to keep a grudge.
The 27-year-old singer is not only famous for her voice, but for her killer songwriting abilities as well.
"She would come up to me at awards shows and say something and walk away, and I would think 'Are we friends, or did she just give me the harshest insult of my life?